Provided by: pdl_2.007-5_amd64 bug

NAME

       PDL::Graphics::PGPLOT::Window - A OO interface to PGPLOT windows

SYNOPSIS

        pdl> use PDL::Graphics::PGPLOT::Window
        pdl> $win = pgwin(Device => '/xs');
        pdl> $a = pdl [1..100]
        pdl> $b = sqrt($a)
        pdl> $win->line($b)
        pdl> $win->hold()
        pdl> $c = sin($a/10)*2 + 4
        pdl> $win->line($c)

       In the following documentation the commands are not shown in their OO versions. This is
       for historical reasons and should not cause too much trouble.

DESCRIPTION

       This package offers a OO interface to the PGPLOT plotting package. This is intended to
       replace the traditional interface in PDL::Graphics::PGPLOT and contains interfaces to a
       large number of PGPLOT routines. Below the usage examples for each function tend to be
       given in the non-OO version for historical reasons. This will slowly be changed, but in
       the meantime refer to the section on OO-interface below to see how to convert the usage
       information below to OO usage (it is totally trivial).

       PDL::Graphics::PGPLOT::Window is an interface to the PGPLOT graphical libraries.  It
       currently supports PGPLOT-5.2 and PGPLOT-5.2-cd2.  The -cd2 version includes RGB output
       and anti-aliasing.

       High-level plotting commands:

        imag       -  Display an image (uses pgimag/pggray/pgrgbi as appropriate)
        fits_imag  -  Display a FITS image in scientific coordinates
        cont       -  Display image as contour map
        fits_cont  -  Display a FITS image in scientific coordinates as a contour map
        vect       -  Display 2 images as a vector field
        fits_vect  -  Display 2 FITS images in sci. coordinates as a vector field
        ctab       -  Load an image colour table
        ctab_info  -  Get information about currently loaded colour table
        line       -  Plot vector as connected points
        tline      -  Plot a collection of vectors as lines
        lines      -  Plot a polyline, multicolor vector [threadable]
        points     -  Plot vector as points
        tpoints    -  Plot a collection of vectors as points [threadable]
        errb       -  Plot error bars
        bin        -  Plot vector as histogram (e.g. bin(hist($data)) )
        hi2d       -  Plot image as 2d histogram (not very good IMHO...)
        tcircle    -  Plot vectors as circles [threadable]
        label_axes -  Print axis titles
        legend     -  Create a legend with different texts, linestyles etc.

       Low-level plotting commands:

        arrow      -  Draw an arrow
        poly       -  Draw a polygon
        rectangle  -  Draw a rectangle
        text       -  Write text in the plot area
        cursor     -  Interactively read cursor positions.
        circle     -  Draw a circle
        ellipse    -  Draw an ellipse.

       Device manipulation commands:

        new           -  Construct a new output device
        pgwin         -  Exported hook to new()
        close         -  Close a PGPLOT output device.
        hold          -  Hold current plot window range - allows overlays etc.
        release       -  Release back to freshly autoscaling for each command.
        held          -  Indicates whether the current window is held.
        focus         -  Set focus to the given device.
        erase         -  Erase the current window (or panel).
        options       -  Get the options set for the present output device.
        id            -  The ID for the device.
        device        -  The device type.
        name          -  The window name.

       Notes: $transform for image/cont etc. is used in the same way as the "TR()" array in the
       underlying PGPLOT FORTRAN routine but is, fortunately, zero-offset. The transform()
       routine can be used to create this piddle.

       For completeness: The transformation array connect the pixel index to a world coordinate
       such that:

        X = tr[0] + tr[1]*i + tr[2]*j
        Y = tr[3] + tr[4]*i + tr[5]*j

   Variable passing and extensions
       In general variables are passed to the pgplot routines by using "get_dataref" to get the
       reference to the values. Before passing to pgplot routines however, the data are checked
       to see if they are in accordance with the format (typically dimensionality) required by
       the PGPLOT routines.  This is done using the routine "checkarg" (internal to PGPLOT). This
       routine checks the dimensionality of the input data. If there are superfluous dimensions
       of size 1 they will be trimmed away until the dimensionality is correct. Example:

       Assume a piddle with dimensions (1,100,1,1) is passed to "line", which expects its inputs
       to be vectors. "checkarg" will then return a piddle with dimensions (100). If instead the
       same piddle was passed to "imag", which requires 2D piddles as output, "checkarg" would
       return a piddle with dimensionality (100, 1) (Dimensions are removed from the start)

       Thus, if you want to provide support for another PGPLOT function, the structure currently
       look like this (there are plans to use the Options package to simplify the options
       parsing):

        # Extract the hash(es) on the commandline
        ($arg, $opt)=_extract_hash(@_);
        <Check the number of input parameters>
        <deal with $arg>
        checkarg($x, 3); # For a hypothetical 3D routine.
        &catch_signals;
        ...
        pgcube($n, $x->get_dataref);
        &release_signals;
        1;

       (the catch_signals/release_signals pair prevent problems with the perl-PGPLOT interface if
       the user hits c-C during an operation).

   Setting options
       All routines in this package take a hash with options as an optional input. This options
       hash can be used to set parameters for the subsequent plotting without going via the
       PGPLOT commands.

       This is implemented such that the plotting settings (such as line width, line style etc.)
       are affected only for that plot, any global changes made, say, with "pgslw()" are
       preserved. Some modifications apply when using the OO interface, see below.

   Alphabetical listing of standard options
       The following options are always parsed. Whether they have any importance depend on the
       routine invoked - e.g. line style is irrelevant for "imag", or the "justify" option is
       irrelevant if the display is on 'hold'.  This is indicated in the help text for the
       commands below.

       The options are not case sensitive and will match for unique substrings, but this is not
       encouraged as obscure options might invalidate what you thought was a unique substring.

       In the listing below examples are given of each option. The actual option can then be used
       in a plot command by specifying it as an argument to the function wanted (it can be placed
       anywhere in the command list).

       E.g:

        $opt={COLOR=>2};
        line $x, $y, $opt; # This will plot a line with red color

       If you are plotting to a hardcopy device then a number of options use a different name:

         HardLW   instead of LineWidth
         HardCH   instead of CharSize
         HardFont instead of Font

         HardAxisColour instead of AxisColour
         HardColour     instead of Colour

       [although I'm not sure when HardColour is actually used]

       align
           If "pix" is set, then images and plots are not stretched to fill the plot area.  the
           "align" string tells how to align them within the available area.  'L' and 'R' shove
           the plot against the left and right edges, respectively; 'B' and 'T' shove the plot
           against the bottom and top edges.  The default is to center the image.  e.g. 'BL' puts
           the image on the bottom left corner, while 'CT' centers the image horizontally while
           placing it at the top of the available plot area.  This defaults to 'BT' for non-
           justified images, to 'CC' for justified images.

       arrow
           This options allows you to set the arrow shape, and optionally size for arrows for the
           vect routine. The arrow shape is specified as a hash with the key FS to set fill
           style, ANGLE to set the opening angle of the arrow head, VENT to set how much of the
           arrow head is cut out and SIZE to set the arrowsize.

           The following

            $opt = {ARROW => {FS=>1, ANGLE=>60, VENT=>0.3, SIZE=>5}};

           will make a broad arrow of five times the normal size.

           Alternatively the arrow can be specified as a set of numbers corresponding to an
           extention to the syntax for pgsah. The equivalent to the above is

            $opt = {ARROW => pdl([1, 60, 0.3, 5})};

           For the latter the arguments must be in the given order, and if any are not given the
           default values of 1, 45, 0.3 and 1.0 respectively will be used.

       arrowsize
           The arrowsize can be specified separately using this option to the options hash. It is
           useful if an arrowstyle has been set up and one wants to plot the same arrow with
           several sizes. Please note that it is not possible to set arrowsize and character size
           in the same call to a plotting function. This should not be a problem in most cases.

            $opt = {ARROWSIZE => 2.5};

       axis
           Set the axis value (see "env").  If you pass in a scalar you set the axis for the
           whole plot.  You can also pass in an array ref for finer control of the axes.

           If you set the option to a scalar value, you get one of a few standard layouts.  You
           can specify them by name or by number:

            EMPTY  (-2) draw no box, axes or labels
            BOX    (-1) draw box only
            NORMAL (0)  draw box and label it with coordinates
            AXES   (1)  same as NORMAL, but also draw (X=0,Y=0) axes
            GRID   (2)  same as AXES, but also draw grid lines
            LOGX   (10) draw box and label X-axis logarithmically
            LOGY   (20) draw box and label Y-axis logarithmically
            LOGXY  (30) draw box and label both axes logarithmically

           When using logarithmic axes ("LOGX", "LOGY" and "LOGXY") you normally need to log the
           data yourself, e.g.

             line $x->log10, $y, {axis=>'LOGX'};

           For your convenience you can put PDL::Graphics::PGPLOT into autolog mode. In this mode
           a call to "line" or "points" will log the data for you and you can pass in the
           unmodified data, e.g.

             autolog(1); # enable automatic logarithm calculation
             line $x, $y, {axis=>'LOGX'}; # automatically displays logged x data

           You can use the function interface to enable autologging:

             autolog(1);

           or use it with a window reference (mode switching on a per window basis)

             $win->autolog(1);

           "autolog" without arguments returns the current autolog setting (0=off, 1=on).

           If you set the "AXIS" option to an array ref, then you can specify the box/axis
           options separately for the horizontal (ordinate; X coordinate; 0th element) and
           vertical (abscissa; Y coordinate; 1st element)) axes.  Each element of the array ref
           should contain a PGPLOT format string.  Presence or absence of specific characters
           flags particular options.  For normal numeric labels, the options are:

             A : draw axis for this dimension.
             B : draw bottom (X) or left (Y) edge of frame.
             C : draw top (X) or right (Y) edge of frame.
             G : draw Grid of vertical (X) or horizontal (Y) lines.
             I : Invert ticks: draw them outside the plot rather than inside.
             L : Label the axis Logarithmically.
             P : Extend ("Project") major tick marks outside the box.
             M : Numeric labels go in the alternate place above (X) or to the
                      right (Y) of the viewport.
             N : Numeric labels go in the usual location below (X) or to the
                      left  (Y) of the viewport
             T : Draw major tick marks at the major coordinate interval.
             S : Draw minor tick marks (subticks).
             V : Orient numeric labels Vertically.  Only applicable to Y.
                      (The default is to write them parallel to the axis.)
             1 : Force decimal labelling, instead of automatic choice
             2 : Force exponential labeling, instead of automatic.

           If you don't specify any axis value at all, the default is ['BCNST','BCNST'] for plots
           and ['BCINST','BCINST'] for images.  (These list ref elements are handed on directly
           to the low-level PGPLOT routines).

           In addition, you can specify that your axis labels should be printed as days, hours,
           minutes, and seconds (ideal for julian dates and delta-t, or for angular quantities).
           You do that by setting additional character flags on the affected axis:

             X : Use HH MM SS.S time labeling rather than conventional numeric
                 labels.  The ordinate is in secsonds. Hours roll over at 24.
             Y : Like 'X' but the hour field runs past 24 if necessary.
             Z : Like 'X' but with a days field too (only shown where nonzero).
             H : Label the numbers with superscript d, h, m, and s symbols.
             D : Label the numbers with superscript o, ', and '' symbols.
             F : Omit first (lowest/leftmost) label; useful for tight layouts.
             O : Omit leading zeroes in numbers under 10 (e.g. " 3h 3m 1.2s"
                 rather than "03h 03m 01.2s").

           For example, to plot a numeric quantity versus Julian day of the year in a standard
           boxed plot with tick marks, you can use ["BNCSTZHO","BCNST"].

       border
           Normally the limits are chosen so that the plot just fits; with this option you can
           increase (or decrease) the limits by either a relative (ie a fraction of the original
           axis width) or an absolute amount.  Either specify a hash array, where the keys are
           "TYPE" (set to 'relative' or 'absolute') and "VALUE" (the amount to change the limits
           by), or set to 1, which is equivalent to

            BORDER => { TYPE => 'rel', VALUE => 0.05 }

       charsize
           Set the character/symbol size as a multiple of the standard size.

            $opt = {CHARSIZE => 1.5}

           The HardCH option should be used if you are plotting to a hardcopy device.

       colour (or color)
           Set the colour to be used for the subsequent plotting. This can be specified as a
           number, and the most used colours can also be specified with name, according to the
           following table (note that this only works for the default colour map):

             0 - WHITE    1 - BLACK     2 - RED      3 - GREEN    4 - BLUE
             5 - CYAN     6 - MAGENTA   7 - YELLOW   8 - ORANGE  14 - DARKGRAY
            16 - LIGHTGRAY

           However there is a much more flexible mechanism to deal with colour.  The colour can
           be set as a 3 or 4 element anonymous array (or piddle) which gives the RGB colours. If
           the array has four elements the first element is taken to be the colour index to
           change. For normal work you might want to simply use a 3 element array with R, G and B
           values and let the package deal with the details. The R,G and B values go from 0 to 1.

           In addition the package will also try to interpret non-recognised colour names using
           the default X11 lookup table, normally using the "rgb.txt" that came with PGPLOT.

           For more details on the handling of colour it is best that the user consults the
           PGPLOT documentation. Further details on the handling of colour can be found in the
           documentation for the internal routine "_set_colour".

           The HardColour option should be used if you are plotting to a hardcopy device [this
           may be untrue?].

       diraxis
           This sets the direction of the axes of a plot or image, when you don't explitly set
           them with the XRange and YRange options.  It's particularly useful when you want (for
           example) to put long wavelengths (larger numbers) on the left hand side of your plot,
           or when you want to plot an image in (RA,dec) coordinates.

           You can use either a scalar or a two-element perl array.  If you set it to 0 (the
           default) then PDL will guess which direction you want to go.  If you set it to a
           positive number, the axis will always increase to the right. If you set it to a
           negative number, the axis will always increase to the left.

           For example, [0,0] is the default, which is usually right.  [1,1] tells PGPLOT to
           always increase the axis values up and to the right.  For a plot of intensity (y-axis)
           versus wavelength (x-axis) you could say [-1,1].

           This option is really only useful if you want to allow autoranging but need to set the
           direction that the axis goes.  If you use the ranging options ("XRange" and "YRange"),
           you can change the direction by changing the order of the maximum and minimum values.
           That direction will override "DirAxis".

       filltype
           Set the fill type to be used by "poly", "circle", "ellipse", and "rectangle" The fill
           can either be specified using numbers or name, according to the following table, where
           the recognised name is shown in capitals - it is case-insensitive, but the whole name
           must be specified.

            1 - SOLID
            2 - OUTLINE
            3 - HATCHED
            4 - CROSS_HATCHED

            $opt = {FILLTYPE => 'SOLID'};

           (see below for an example of hatched fill)

       font
           Set the character font. This can either be specified as a number following the PGPLOT
           numbering or name as follows (name in capitals):

            1 - NORMAL
            2 - ROMAN
            3 - ITALIC
            4 - SCRIPT

           (Note that in a string, the font can be changed using the escape sequences "\fn",
           "\fr", "\fi" and "\fs" respectively)

            $opt = {FONT => 'ROMAN'};

           gives the same result as

            $opt = {FONT => 2};

           The HardFont option should be used if you are plotting to a hardcopy device.

       hatching
           Set the hatching to be used if either fillstyle 3 or 4 is selected (see above) The
           specification is similar to the one for specifying arrows.  The arguments for the
           hatching is either given using a hash with the key ANGLE to set the angle that the
           hatch lines will make with the horizontal, SEPARATION to set the spacing of the hatch
           lines in units of 1% of "min(height, width)" of the view surface, and PHASE to set the
           offset the hatching. Alternatively this can be specified as a 1x3 piddle
           "$hatch=pdl[$angle, $sep, $phase]".

            $opt = {FILLTYPE => 'HATCHED',
                    HATCHING => {ANGLE=>30, SEPARATION=>4}};

           Can also be specified as

            $opt = {FILL=> 'HATCHED', HATCH => pdl [30,4,0.0]};

           For another example of hatching, see "poly".

       justify
           If "justify" is set true, then the plot axes are shrunk to fit the plot or image and
           it specifies the aspect ratio of pixel coordinates in the plot or image.  Setting
           justify=>1 will produce a correct-aspect-ratio, shrink-wrapped image or plot; setting
           justify=>0.5 will do the same thing but with a short and fat plot.  The difference
           between "justify" and "pix" is that "pix" does not affect the shape of the axes
           themselves.

       linestyle
           Set the line style. This can either be specified as a number following the PGPLOT
           numbering:

            1 - SOLID line
            2 - DASHED
            3 - DOT-DASH-dot-dash
            4 - DOTTED
            5 - DASH-DOT-DOT-dot

           or using name (as given in capitals above).  Thus the following two specifications
           both specify the line to be dotted:

            $opt = {LINESTYLE => 4};
            $varopt = {LINESTYLE => 'DOTTED'};

           The names are not case sensitive, but the full name is required.

       linewidth
           Set the line width. It is specified as a integer multiple of 0.13 mm.

            $opt = {LINEWIDTH => 10}; # A rather fat line

           The HardLW option should be used if you are plotting to a hardcopy device.

       pitch
           Sets the number of data pixels per inch on the output device.  You can set the "unit"
           (see below) to change this to any other PGPLOT unit (millimeters, pixels, etc.).
           Pitch is device independent, so an image should appear exactly the same size (e.g.
           "Pitch=>100" is 100 dpi) regardless of output device.

       pix Sets the pixel aspect ratio height/width.  The height is adjusted to the correct
           ratio, while maintaining any otherwise-set pitch or scale in the horizontal direction.
           Larger numbers yield tall, skinny pixels; smaller numbers yield short, fat pixels.

       scale
           Sets the number of output display pixels per data pixel.  You can set the "unit" (see
           below) to change this to number of PGPLOT units (inches, millimeters, etc.) per data
           pixel.  "scale" is deprecated, as it is not device-independent; but it does come in
           handy for quick work on digital displays, where aliasing might otherwise interfere
           with image interpretation.  For example, "scale=>1" displays images at their native
           resolution.

       Panel
           It is possible to define multiple plot ``panels'' with in a single window (see the
           NXPanel and NYPanel options in the constructor).  You can explicitly set in which
           panel most plotting commands occur, by passing either a scalar or an array ref into
           the "Panel" option.  There is also a panel method, but its use is deprecated because
           of a wart with the PGPLOT interface.

       plotting & imaging range
           Explicitly set the plot range in x and y. X-range and Y-range are set separately via
           the aptly named options "XRange" and "YRange". If omitted PGPLOT selects appropriate
           defaults (minimum and maximum of the data range in general). These options are ignored
           if the window is on hold.

             line $x, $y, {xr => [0,5]}; # y-range uses default
             line $x, $y, {XRange => [0,5], YRange => [-1,3]}; # fully specified range
             imag $im, {XRange => [30,50], YRange=>[-10,30]};
             fits_imag $im, {XRange=>[-2,2], YRange=>[0,1]};

           Imaging requires some thought if you don't want to lose a pixel off the edge of the
           image.  Pixels are value-centered (they are centered on the coordinate whose value
           they represent), so the appropriate range to plot the entirety of a 100x100 pixel
           image is "[-0.5,99.5]" on each axis.

OBJECT-ORIENTED INTERFACE

       This section will briefly describe how the PDL::Graphics::PGPLOT::Window package can be
       used in an object-oriented (OO) approach and what the advantages of this would be. We will
       start with the latter

       Multiple windows.
           For the common user it is probably most interesting to use the OO interface when
           handling several open devices at the same time. If you have one variable for each plot
           device it is easier to distribute commands to the right device at the right time. This
           is the angle we will take in the rest of this description.

       Coding and abstraction
           At a more fundamental level it is desirable to approach a situation where it is
           possible to have a generic plotting interface which gives access to several plotting
           libraries, much as PGPLOT gives access to different output devices. Thus in such a
           hypothetical package one would say:

             my $win1 = Graphics::new('PGPLOT', {Device => '/xs'});
             my $win2 = Graphics::new('gnuplot', {Background => 'Gray'};

           From a more practical point of of view such abstraction also comes in handy when you
           write a large program package and you do not want to import routines nilly-willy in
           which case an OO approach with method calls is a lot cleaner.

           The pgwin exported constructor, arguably, breaks this philosophy; hopefully it will
           ``wither away'' when other compatible modules are available.

       Anyway, enough philosophizing, let us get down to Earth and give some examples of the use
       of OO PGPLOT. As an example we will take Odd (which happens to be a common Norwegian name)
       who is monitoring the birth of rabbits in O'Fib-o-nachy's farm (alternatively he can of
       course be monitoring processes or do something entirely different). Odd wants the user to
       be able to monitor both the birth rates and accumulated number of rabbits and the spatial
       distribution of the births. Since these are logically different he chooses to have two
       windows open:

         $rate_win = PDL::Graphics::PGPLOT::Window->new(Device => '/xw',
                     Aspect => 1, WindowWidth => 5, NXPanel => 2);

         $area_win = PDL::Graphics::PGPLOT::Window->new(Device => '/xw',
                     Aspect => 1, WindowWidth => 5);

       See the documentation for new below for a full overview of the options you can pass to the
       constructor.

       Next, Odd wants to create plotting areas for subsequent plots and maybe show the expected
       theoretical trends

         $rate_win->env(0, 10, 0, 1000, {XTitle => 'Days', YTitle => '#Rabbits'});
         $rate_win->env(0, 10, 0, 100, {Xtitle=>'Days', Ytitle => 'Rabbits/day'});

         $area_win->env(0, 1, 0, 1, {XTitle => 'Km', Ytitle => 'Km'});
         # And theoretical prediction.
         $rate_win->line(sequence(10), fibonacci(10), {Panel => [1, 1]});

       That is basically it. The commands should automatically focus the relevant window. Due to
       the limitations of PGPLOT this might however lead you to plot in the wrong panel... The
       package tries to be smart and do this correctly, but might get it wrong at times.

STATE and RECORDING

       A new addition to the graphics interface is the ability to record plot commands. This can
       be useful when you create a nice-looking plot on the screen that you want to re-create on
       paper for instance. Or if you want to redo it with slightly changed variables for
       instance. This is still under development and views on the interface are welcome.

       The functionality is somewhat detached from the plotting functions described below so I
       will discuss them and their use here.

       Recording is off by default. To turn it on when you create a new device you can set the
       "Recording" option to true, or you can set the $PDL::Graphics::PGPLOT::RECORDING variable
       to 1. I recommend doing the latter in your ".perldlrc" file at least since you will often
       have use for recording in the perldl or pdl2 script.

   Use of recording
       The recording is meant to help you recreate a plot with new data or to a different device.
       The most typical situation is that you have created a beautiful plot on screen and want to
       have a Postscript file with it. In the dreary old world you needed to go back and execute
       all commands manually, but with this wonderful new contraption, the recorder, you can just
       replay your commands:

         dev '/xs', {Recording => 1}
         $x = sequence(10)
         line $x, $x**2, {Linestyle => 'Dashed'}
         $s = retrieve_state() # Get the current tape out of the recorder.
         dev '/cps'
         replay $s

       This should result in a "pgplot.ps" file with a parabola drawn with a dashed line. Note
       the command "retrieve_state" which retrieves the current state of the recorder and return
       an object (of type PDL::Graphics::State) that is used to replay commands later.

   Controlling the recording
       Like any self-respecting recorder you can turn the recorder on and off using the
       "turn_on_recording" and "turn_off_recording" respectively.  Likewise you can clear the
       state using the "clear_state" command.

         $w=PDL::Graphics::PGPLOT::Window->new(Device => '/xs');
         $w->turn_on_recording;
         $x=sequence(10); $y=$x*$x;
         $w->line($x, $y);
         $w->turn_off_recording;
         $w->line($y, $x);
         $w->turn_on_recording;
         $w->line($x, $y*$x);
         $state = $w->retrieve_state();

       We can then replay $state and get a parabola and a cubic plot.

         $w->replay($state);

   Tips and Gotchas!
       The data are stored in the state object as references to the real data. This leads to one
       good and one potentially bad consequence:

       The good is that you can create the plot and then subsequently redo the same plot using a
       different set of data. This is best explained by an example. Let us first create a simple
       gradient image and get a copy of the recording:
             $im = sequence(10,10)
             imag $im
             $s=retrieve_state

           Now this was a rather dull plot, and in reality we wanted to show an image using
           "rvals". Instead of re-creating the plot (which of course here would be the simplest
           option) we just change $im:

             $im -= sequence(10,10)
             $im += rvals(10,10)

           Now replay the commands

             replay $s

           And hey presto! A totally different plot. Note however the trickery required to avoid
           losing reference to $im

       This takes us immediately to the major problem with the recording though. Memory leakage!
       Since the recording keeps references to the data it can keep data from being freed (zero
       reference count) when you expect it to be. For instance, in this example, we lose totally
       track of the original $im variable, but since there is a reference to it in the state it
       will not be freed
             $im = sequence(1000,1000)
             imag $im
             $s = retrieve_state
             $im = rvals(10,10)

           Thus after the execution of these commands we still have a reference to a 1000x1000
           array which takes up a lot of memory...

           The solution is to call "clear" on the state variable:

             $s->clear()

           (This is done automatically if the variable goes out of scope). I forsee this problem
           to most acute when working on the "perldl" or "pdl2" command line, but since this is
           exactly where the recording is most useful the best advice is just to be careful and
           call clear on state variables.

           If you are working with scripts and use large images for instance I would instead
           recommend that you do not turn on recording unless you need it.

FUNCTIONS

       A more detailed listing of the functions and their usage follows. For all functions we
       specify which options take effect and what other options exist for the given function. The
       function descriptions below are all given for the non-OO usage for historical reasons, but
       since the conversion to an OO method is trivial there is no major need for concern.
       Whenever you see a function example of the form

         Usage: a_simple_function($x, $y, $z [, $opt]);

       and you wish to use the OO version, just let your mind read the above line as:

         Usage: $win->a_simple_function($x, $y, $z [, $opt]);

       where $win is a PDL::Graphics::PGPLOT::Window object. That is all.

   Window control functions.
   pgwin
       Exported constructor for PGPLOT object/device/plot window.

        Usage: pgwin($opt);
        Usage: pgwin($option->$value,...);
        Usage: pgwin($device);

       Parameters are passed on to new() and can either be specified by hash reference or as a
       list.

       See the documentation fo PDL::Graphics::PGPLOT::Window::new for details.

       Because pgwin is a convenience function, you can specify the device by passing in a single
       non-ref parameter.  For even further convenience, you can even omit the '/' in the device
       specifier, so these two lines deliver the same result:

           $a = pgwin(gif);
           $a = new PDL::Graphics::PGPLOT::Window({Dev=>'/gif'});

   new
       Constructor for PGPLOT object/device/plot window.

         Usage: PDL::Graphics::PGPLOT::Window->new($opt);
         Usage: PDL::Graphics::PGPLOT::Window->new($option=>$value,...);

       Options to new() can either be specified via a reference to a hash

         $win = PDL::Graphics::PGPLOT::Window->new({Dev=>'/xserve',ny=>2});

       or directly, as an array

         # NOTE: no more {} !
         $win = PDL::Graphics::PGPLOT::Window->new(Dev=>'/xserve',ny=>2);

       The following lists the recognised options:

       AspectRatio
           The aspect ratio of the image, in the sense vertical/horizontal.  See the discussion
           on size setting.

       Device
           The type of device to use. The syntax of this is the one used by PGPLOT.

       Hold
           Hold the plot window so that subsequent plots can plot over existing plots.  This can
           be adjusted with the "hold()" and "release()" methods.

       NXPanel
           The number of panels in the X-direction

       NYPanel
           The number of panels in the Y-direction

       Size
           Yet another way to identify the plot window size -- this takes a scalar or an array
           ref containing one, two, or three numbers.  One number gives you a square window.  Two
           gives you a rectangular window "(X,Y)".  Three lets you specify the unit compactly
           (e.g. "[<X>,<Y>,1]" for inches, "[<X>,<Y>,2]" for mm) but is deprecated in favor of
           using the "Unit" option.  See the discussion on size setting.

       Unit
           The unit to use for size setting.  PGPLOT accepts inch, mm, or pixel.  The default
           unit is inches for historical reasons, but you can choose millimeters or (God forbid)
           pixels as well.  String or numeric specifications are OK (0=normalized, 1=inches,
           2=mm, 3=pixels).  Normalized units make no sense here and are not accepted.  Ideally
           someone will one day hook this into the CPAN units parser so you can specify window
           size in rods or attoparsecs.

       WindowName
           The name to give to the window. No particular use is made of this at present.  It
           would be great if it was possible to change the title of the window frame.

       WindowWidth
           The width of the window in inches (or the specified Unit).  See the discussion on size
           setting.

       WindowXSize and WindowYSize
           The width and height of the window in inches (or the specified Unit).  See the
           discussion on size setting.

       An important point to note is that the default values of most options can be specified by
       passing these to the constructor. All general options (common to several functions) can be
       adjusted in such a way, but function specific options can not be set in this way (this is
       a design limitation which is unlikely to be changed).

       Thus the following call will set up a window where the default axis colour will be yellow
       and where plot lines normally have red colour and dashed linestyle.

         $win = PDL::Graphics::PGPLOT::Window->new(Device => '/xs',
                 AxisColour => 'Yellow', Colour => 'Red', LineStyle => 'Dashed');

       Size setting: There are a gazillion ways to set window size, in keeping with TIMTOWTDI.
       In general you can get away with passing any unique combination of an "<X>" size, a
       "<Y>"size, and/or an aspect ratio.  In increasing order of precedence, the options are:
       ("Units", "AspectRatio", "WindowWidth", "Window<X,Y>Size", "Size").

       So if you specify an AspectRatio *and* an X and a Y coordinate, the AspectRatio is
       ignored.  Likewise, if you specify Units and a three-component Size, the Units option is
       ignored in favor of the numeric unit in the Size.

       If you don't specify enough information to set the size of the window, you get the default
       pane size and shape for that device.

   close
       Close a plot window

         Usage: $win->close()

       Close the current window. This does not necessarily mean that the window is removed from
       your screen, but it does ensure that the device is closed.

       A message will be printed to STDOUT giving the name of the file created if the plot was
       made to a hardcopy device and $PDL::verbose is true.

   held
       Check if a window is on hold

         $is_held = $win->held();

       Function to check whether the window is held or not.

   hold
       Hold the present window.

        Usage: $win->hold()

       Holds the present window so that subsequent plot commands overplots.

   panel
       Switch to a different panel

         $win->panel(<num>);

       Move to a different panel on the plotting surface. Note that you will need to erase it
       manually if that is what you require.

       This routine currently does something you probably don't want, and hence is deprecated for
       most use:  if you say

         $win->panel(1);
         $win->imag($image);

       then $image will actually be displayed in panel 2.  That's because the main plotting
       routines such as line and imag all advance the panel when necessary.  Instead, it's better
       to use the Panel option within plotting commands, if you want to set the panel explicitly.

   release
       Release a plot window.

          $win->release()

       Release a plot window so that subsequent plot commands move to the next panel or erase the
       plot and create a new plot.

   erase
       Erase plot

         $win->erase($opt);

       Erase a plot area. This accepts the option "Panel" or alternatively a number or array
       reference which makes it possible to specify the panel to erase when working with several
       panels.

   Plotting functions
   env
       Define a plot window, and put graphics on 'hold'

        $win->env( $xmin, $xmax, $ymin, $ymax, [$justify, $axis] );
        $win->env( $xmin, $xmax, $ymin, $ymax, [$options] );

       $xmin, $xmax, $ymin, $ymax are the plot boundaries.  $justify is a boolean value (default
       is 0); if true the axes scales will be the same (see "justify").  $axis describes how the
       axes should be drawn (see "axis") and defaults to 0.

       If the second form is used, $justify and $axis can be set in the options hash, for
       example:

        $win->env( 0, 100, 0, 50, {JUSTIFY => 1, AXIS => 'GRID',
                                   CHARSIZE => 0.7} );

       In addition the following options can also be set for "env":

       PlotPosition
           The position of the plot on the page relative to the view surface in normalised
           coordinates as an anonymous array. The array should contain the lower and upper
           X-limits and then the lower and upper Y-limits. To place two plots above each other
           with no space between them you could do

             $win->env(0, 1, 0, 1, {PlotPosition => [0.1, 0.5, 0.1, 0.5]});
             $win->env(5, 9, 0, 8, {PlotPosition => [0.1, 0.5, 0.5, 0.9]});

       Axis, Justify, Border
           See the description of general options for these options.

       AxisColour
           Set the colour of the coordinate axes.

       XTitle, YTitle, Title, Font, CharSize
           Axes titles and the font and size to print them.

   label_axes
       Label plot axes

         $win->label_axes(<xtitle>, <ytitle>, <plot title>, $options);

       Draw labels for each axis on a plot.

   imag
       Display an image (uses "pgimag()"/"pggray()" as appropriate)

        $win->imag ( $image,  [$min, $max, $transform], [$opt] )

       NOTES

       $transform for image/cont etc. is used in the same way as the "TR()" array in the
       underlying PGPLOT FORTRAN routine but is, fortunately, zero-offset. The transform()
       routine can be used to create this piddle.

       If $image is two-dimensional, you get a grey or pseudocolor image using the scalar values
       at each X,Y point.  If $image is three-dimensional and the third dimension has order 3,
       then it is treated as an RGB true-color image via rgbi.

       There are several options related to scaling.  By default, the image is scaled to fit the
       PGPLOT default viewport on the screen.  Scaling, aspect ratio preservation, and 1:1 pixel
       mapping are available.  (1:1 pixel mapping is useful for avoiding display artifacts, but
       it's not recommended for final output as it's not device-independent.)

       Here's an additional complication: the "pixel" stuff refers not (necessarily) to normal
       image pixels, but rather to transformed image pixels.  That is to say, if you feed in a
       transform matrix via the "TRANSFORM" option, the "PIX", "SCALE", etc. options all refer to
       the transformed coordinates and not physical image pixels.  That is a Good Thing because
       it, e.g., lets you specify plate scales of your output plots directly!  See fits_imag for
       an example application.  If you do not feed in a transform matrix, then the identity
       matrix is applied so that the scaling options refer to original data pixels.

       To draw a colour bar (or wedge), either use the "DrawWedge" option, or the "draw_wedge()"
       routine (once the image has been drawn).

       Options recognised:

       ITF
          the image transfer function applied to the pixel values.  It may be one of 'LINEAR',
          'LOG', 'SQRT' (lower case is acceptable). It defaults to 'LINEAR'.

       MIN
          Sets the minimum value to be used for calculation of the color-table stretch.

       MAX
          Sets the maximum value for the same.

       RANGE
          A more compact way to specify MIN and MAX, as a list: you can say "Range=>[0,10]" to
          scale the color table for brightness values between 0 and 10 in the iamge data.

       CRANGE
          Image values between MIN and MAX are scaled to an interval in normalized color domain
          space, on the interval [0,1], before lookup in the window's color table. CRANGE lets
          you use only a part of the color table by specifying your own range -- e.g. if you say
          "CRange=>[0.25,0.75]" then only the middle half of the pseudocolor space will be used.
          (See the writeup on ctab().)

       TRANSFORM
          The PGPLOT transform 'matrix' as a 6x1 vector for display

       DrawWedge
          set to 1 to draw a colour bar (default is 0)

       Wedge
          see the draw_wedge() routine

       The following standard options influence this command:

        AXIS, BORDER, JUSTIFY, SCALE, PIX, PITCH, ALIGN, XRANGE, YRANGE

          To see an image with maximum size in the current window, but square
          pixels, say:
                $win->imag( $a, { PIX=>1 } );
          An alternative approach is to try:
                $win->imag( $a, { JUSTIFY=>1 } );
          To see the same image, scaled 1:1 with device pixels, say:
                $win->imag( $a, { SCALE=>1 } );
          To see an image made on a device with 1:2 pixel aspect ratio, with
          X pixels the same as original image pixels, say
                $win->imag( $a, { PIX=>0.5, SCALE=>2 } );
          To display an image at 100 dpi on any device, say:
                $win->imag( $a, { PITCH=>100 } );
          To display an image with 100 micron pixels, say:
                $win->imag( $a, { PITCH=>10, UNIT=>'mm' } );

   imag1
       Display an image with correct aspect ratio

        $win->imag1 ( $image, [$min, $max, $transform], [$opt] )

       This is syntactic sugar for

         $win->imag( { PIX=>1, ALIGN=>'CC' } );

   rgbi
       Display an RGB color image

       The calling sequence is exactly like "imag", except that the input image must have three
       dimensions: "N x M x 3".  The last dimension is the (R,G,B) color value.  This routine
       requires pgplot 5.3devel or later.  Calling rgbi explicitly is not necessary, as calling
       image with an appropriately dimensioned RGB triplet makes it fall through to rgbi.

   fits_imag
       Display a FITS image with correct axes

         $win->fits_imag( image,  [$min, $max], [$opt] );

       NOTES

       Titles:
          Currently fits_imag also generates titles for you by default and appends the FITS
          header scientific units if they're present.  So if you say

            $pdl->hdr->{CTYPE1} = "Flamziness";
            $pdl->hdr->{CUNIT1} = "milliBleems";
            $win->fits_imag($pdl);

          then you get an X title of "Flamziness (milliBleems)".  But you can (of course)
          override that by specifying the XTitle and YTitle switches:

            $win->fits_imag($pdl,{Xtitle=>"Arbitrary"});

          will give you "Arbitrary" as an X axis title, regardless of what's in the header.

       Scaling and aspect ratio:
          If CUNIT1 and CUNIT2 (or, if they're missing, CTYPE1 and CTYPE2) agree, then the
          default pixel aspect ratio is 1 (in scientific units, NOT in original pixels).  If they
          don't agree (as for a spectrum) then the default pixel aspect ratio is adjusted
          automatically to match the plot viewport and other options you've specified.

          You can override the image scaling using the SCALE, PIX, or PITCH options just as with
          the imag() method -- but those parameters refer to the scientific coordinate system
          rather than to the pixel coordinate system (e.g. "PITCH=>100" means "100 scientific
          units per inch", and "SCALE=>1" means "1 scientific unit per device pixel").  See the
          imag() writeup for more info on these options.

          The default value of the "ALIGN" option is 'CC' -- centering the image both vertically
          and horizontally.

       Axis direction:
          By default, fits_imag tries to guess which direction your axes are meant to go (left-
          to-right or right-to-left) using the CDELT keywords: if "CDELT" is negative, then
          rather than reflecting the image fits_imag will plot the X axis so that the highest
          values are on the left.

          This is the most convenient behavior for folks who use calibrated (RA,DEC) images, but
          it is technically incorrect.  To force the direction, use the DirAxis option.  Setting
          "DirAxis=>1" (abbreviated "di=>1") will force the scientific axes to increase to the
          right, reversing the image as necessary.

       Color wedge:
          By default fits_imag draws a color wedge on the right; you can explicitly set the
          "DrawWedge" option to 0 to avoid this.  Use the "WTitle" option to set the wedge title.

       Alternate WCS coordinates:
          The default behaviour is to use the primary/default WCS information in the FITS header
          (i.e. the "CRVAL1","CRPIX1",... keywords). The Greisen et al. standard
          (<http://fits.cv.nrao.edu/documents/wcs/wcs.html>) allows alternative/additional
          mappings to be included in a header; these are denoted by the letters "A" to "Z". If
          you know that your image contains such a mapping then you can use the "WCS" option to
          select the appropriate letter. For example, if you had read in a Chandra image created
          by the CIAO software package then you can display the image in the "physical"
          coordinate system by saying:

            $win->fits_imag( $pdl, { wcs => 'p' } );

          The identity transform is used if you select a mapping for which there is no
          information in the header.  Please note that this suport is experimental and is not
          guaranteed to work correctly; please see the documentation for the _FITS_tr routine for
          more information.

   fits_rgbi
       Display an RGB FITS image with correct axes

         $win->fits_rgbi( image, [$min,$max], [$opt] );

       Works exactly like fits_imag, but the image must be in (X,Y,RGB) form.  Only the first two
       axes of the FITS header are examined.

   fits_cont
       Draw contours of an image, labelling the axes using the WCS information in the FITS header
       of the image.

         $win->fits_cont( image, [$contours, $transform, $misval], [$opt] )

       Does the same thing for the cont routine that fits_imag does for the imag routins.

   draw_wedge
       Add a wedge (colour bar) to an image.

        $win->draw_wedge( [$opt] )

       Adds a wedge - shows the mapping between colour and value for a pixel - to the current
       image.  This can also be achieved by setting "DrawWedge" to 1 when calling the "imag"
       routine.

       The colour and font size are the same as used to draw the image axes (although this will
       probably fail if you did it yourself).  To control the size and location of the wedge, use
       the "Wedge" option, giving it a hash reference containing any of the following:

       Side
           Which side of the image to draw the wedge: can be one of 'B', 'L', 'T', or 'R'.
           Default is 'R'.

       Displacement
           How far from the egde of the image should the wedge be drawn, in units of character
           size. To draw within the image use a negative value. Default is 1.5.

       Width
           How wide should the wedge be, in units of character size.  Default is 2.

       Label
           A text label to be added to the wedge.  If set, it is probably worth increasing the
           "Width" value by about 1 to keep the text readable.  Default is ''.  This is
           equivalent to the "WTitle" option to imag, fits_imag, and similar methods.

       ForeGround (synonym Fg)
           The pixel value corresponding to the "maximum" colour.  If "undef", uses the value
           used by "imag" (recommended choice).  Default is "undef".

       BackGround (synonym Bg)
           The pixel value corresponding to the "minimum" colour.  If "undef", uses the value
           used by "imag" (recommended choice).  Default is "undef".

        $a = rvals(50,50);
        $win = PDL::Graphics::PGPLOT::Window->new();
        $win->imag( $a, { Justify => 1, ITF => 'sqrt' } );
        $win->draw_wedge( { Wedge => { Width => 4, Label => 'foo' } } );
        # although the following might be more sensible
        $win->imag( $a, { Justify => 1, ITF => 'sqrt', DrawWedge => 1,
            Wedge => { Width => 4, Label => 'foo'} } );

   ctab
       Load an image colour table.

        Usage:

          ctab ( $name, [$contrast, $brightness] ) # Builtin col table
          ctab ( $ctab, [$contrast, $brightness] ) # $ctab is Nx4 array
          ctab ( $levels, $red, $green, $blue, [$contrast, $brightness] )
          ctab ( '', $contrast, $brightness ) # use last color table

       Note: See PDL::Graphics::LUT for access to a large number of colour tables.

       Notionally, all non-RGB images and vectors have their colors looked up in the window's
       color table.  Colors in images and such are scaled to a normalized pseudocolor domain on
       the line segment [0,1]; the color table is a piecewise linear function that maps this one-
       dimensional scale to the three-dimensional normalized RGB color space [0,1]^3.

       You can specify specific indexed colors by appropriate use of the (levels,red,green,blue)
       syntax -- but that is deprecated, since the actual available number of colors can change
       depending on the output device.  (Someone needs to write a specific hardware-dependent
       lookup table interface).

       See also imag for a description of how to use only part of the color table for a
       particular image.

   ctab_info
       Return information about the currently loaded color table

   autolog
       Turn on automatic logarithmic scaling in "line" and "points"

         Usage:  autolog([0|1]);

       Setting the argument to 1 turns on automatic log scaling and setting it to zero turns it
       off again. The function can be used in both the object oriented and standard interface. To
       learn more, see the documentation for the axis option.

          my $win = PDL::Graphics::PGPLOT::Window->new(dev=>'/xserve');
          my $x=sequence(10);
          my $y=$x*$x+1;

          $win->autolog(1);
          $win->line($x,$y, {Axis => 'LogY'});

   line
       Plot vector as connected points

       If the 'MISSING' option is specified, those points in the $y vector which are equal to the
       MISSING value are not plotted, but are skipped over.  This allows one to quickly draw
       multiple lines with one call to "line", for example to draw coastlines for maps.

        Usage: line ( [$x,] $y, [$opt] )

       The following standard options influence this command:

        AXIS, BORDER, COLO(U)R, LINESTYLE, LINEWIDTH, MISSING,
        JUSTIFY, SCALE, PITCH, PIX, ALIGN

        $x = sequence(10)/10.;
        $y = sin($x)**2;
        # Draw a red dot-dashed line
        line $x, $y, {COLOR => 'RED', LINESTYLE=>3};

   lines
       Plot a list of vectors as discrete sets of connected points

       This works much like line, but for discrete sets of connected points.  There are two ways
       to break lines: you can pass in x/y coordinates just like in line, but with an additional
       "pen" piddle that indicates whether the pen is up or down on the line segment following
       each point (so you set it to zero at the end of each line segment you want to draw);  or
       you can pass in an array ref containing a list of single polylines to draw.

       Happily, there's extra meaning packed into the "pen" piddle: it multiplies the COLO(U)R
       that you set, so if you feed in boolean values you get what you expect -- but you can also
       feed in integer or floating-point values to get multicolored lines.

       Furthermore, the sign bit of "pen" can be used to draw hairline segments: if "pen" is
       negative, then the segment is drawn as though it were positive but with LineWidth and
       HardLW set to 1 (the minimum).

       Equally happily, even if you are using the array ref mechanism to break your polylines you
       can feed in an array ref of "pen" values to take advantage of the color functionality or
       further dice your polylines.

       Note that, unlike line, "lines" has no no specify-$y-only calling path.  That's because
       "lines" is intended more for line art than for plotting, so you always have to specify
       both $x and $y.

       Infinite or bad values are ignored -- that is to say, if your vector contains a non-finite
       point, that point breaks the vector just as if you set pen=0 for both that point and the
       point before it.

        Usage: $w->lines( $x, $y, [$pen], [$opt] );
               $w->lines( $xy, [$pen], [$opt] );
               $w->lines( \@xvects, \@yvects, [\@pen], [$opt] );
               $w->lines( \@xyvects, [\@pen], [$opt] );

       The following standard options influence this command:
        AXIS, BORDER, COLO(U)R, LINESTYLE, LINEWIDTH, MISSING,
        JUSTIFY, SCALE, PITCH, PIX, ALIGN

       CAVEAT:

       Setting "pen" elements to 0 prevents drawing altogether, so you can't use that to draw in
       the background color.

   points
       Plot vector as points

        Usage: points ( [$x,] $y, [$symbol(s)], [$opt] )

       Options recognised:

          SYMBOL - Either a piddle with the same dimensions as $x, containing
                   the symbol associated to each point or a number specifying
                   the symbol to use for every point, or a name specifying the
                   symbol to use according to the following (recognised name in
                    capital letters):
                    0 - SQUARE   1 - DOT     2 - PLUS     3 - ASTERISK
                    4 - CIRCLE   5 - CROSS   7 - TRIANGLE 8 - EARTH
                    9 - SUN     11 - DIAMOND 12- STAR
        PLOTLINE - If this is >0 a line will be drawn through the points.

       The following standard options influence this command:

        AXIS, BORDER, CHARSIZE, COLOUR, LINESTYLE, LINEWIDTH,
        JUSTIFY, SCALE, PIX, PITCH, ALIGN

       "SymbolSize" allows to adjust the symbol size, it defaults to CharSize.

       The "ColorValues" option allows one to plot XYZ data with the Z axis mapped to a color
       value.  For example:

        use PDL::Graphics::LUT;
        ctab(lut_data('idl5')); # set up color palette to 'idl5'
        points ($x, $y, {ColorValues => $z});

        $y = sequence(10)**2+random(10);
        # Plot blue stars with a solid line through:
        points $y, {PLOTLINE => 1, COLOUR => BLUE, symbol => STAR}; # case insensitive

   errb
       Plot error bars (using "pgerrb()")

       Usage:

        errb ( $y, $yerrors, [$opt] )
        errb ( $x, $y, $yerrors, [$opt] )
        errb ( $x, $y, $xerrors, $yerrors, [$opt] )
        errb ( $x, $y, $xloerr, $xhierr, $yloerr, $yhierr, [$opt])

       Any of the error bar parameters may be "undef" to omit those error bars.

       Options recognised:

          TERM - Length of terminals in multiples of the default length
        SYMBOL - Plot the datapoints using the symbol value given, either
                 as name or number - see documentation for 'points'

       The following standard options influence this command:

        AXIS, BORDER, CHARSIZE, COLOUR, LINESTYLE, LINEWIDTH,
        JUSTIFY, SCALE, PIX, PITCH, ALIGN

        $y = sequence(10)**2+random(10);
        $sigma=0.5*sqrt($y);
        errb $y, $sigma, {COLOUR => RED, SYMBOL => 18};

        # plot X bars only
        errb( $x, $y, $xerrors, undef );

        # plot negative going bars only
        errb( $x, $y, $xloerr, undef, $yloerr, undef );

   cont
       Display image as contour map

        Usage: cont ( $image,  [$contours, $transform, $misval], [$opt] )

       Notes: $transform for image/cont etc. is used in the same way as the "TR()" array in the
       underlying PGPLOT FORTRAN routine but is, fortunately, zero-offset. The transform()
       routine can be used to create this piddle.

       Options recognised:

           CONTOURS - A piddle with the contour levels
             FOLLOW - Follow the contour lines around (uses pgcont rather than
                      pgcons) If this is set >0 the chosen linestyle will be
                      ignored and solid line used for the positive contours
                      and dashed line for the negative contours.
             LABELS - An array of strings with labels for each contour
        LABELCOLOUR - The colour of labels if different from the draw colour
                      This will not interfere with the setting of draw colour
                      using the colour keyword.
            MISSING - The value to ignore for contouring
          NCONTOURS - The number of contours wanted for automatical creation,
                      overridden by CONTOURS
          TRANSFORM - The pixel-to-world coordinate transform vector

       The following standard options influence this command:

        AXIS, BORDER, COLOUR, LINESTYLE, LINEWIDTH,
        JUSTIFY, SCALE, PIX, PITCH, ALIGN

        $x=sequence(10,10);
        $ncont = 4;
        $labels= ['COLD', 'COLDER', 'FREEZING', 'NORWAY']
        # This will give four blue contour lines labelled in red.
        cont $x, {NCONT => $ncont, LABELS => $labels, LABELCOLOR => RED,
                  COLOR => BLUE}

   bin
       Plot vector as histogram (e.g. "bin(hist($data))")

        Usage: bin ( [$x,] $data )

       Options recognised:

        CENTRE - (default=1) if true, the x values denote the centre of the
                 bin otherwise they give the lower-edge (in x) of the bin
        CENTER - as CENTRE

       The following standard options influence this command:

        AXIS, BORDER, COLOUR, JUSTIFY, LINESTYLE, LINEWIDTH

   hi2d
       Plot image as 2d histogram (not very good IMHO...)

        Usage: hi2d ( $image, [$x, $ioff, $bias], [$opt] )

       Options recognised:

        IOFFSET - The offset for each array slice. >0 slants to the right
                                                   <0 to the left.
           BIAS - The bias to shift each array slice up by.

       The following standard options influence this command:

        AXIS, BORDER, JUSTIFY, SCALE, PIX, PITCH, ALIGN

       Note that meddling with the "ioffset" and "bias" often will require you to change the
       default plot range somewhat. It is also worth noting that if you have TriD working you
       will probably be better off using mesh3d or a similar command - see the
       PDL::Graphics::TriD module.

        $r=sequence(100)/50-1.0;
        $y=exp(-$r**2)*transpose(exp(-$r**2))
        hi2d $y, {IOFF => 1.5, BIAS => 0.07};

   arrow
       Plot an arrow

        Usage: arrow($x1, $y1, $x2, $y2, [, $opt]);

       Plot an arrow from "$x1, $y1" to "$x2, $y2". The arrow shape can be set using the option
       "Arrow". See the documentation for general options for details about this option (and the
       example below):

       Example:

         arrow(0, 1, 1, 2, {Arrow => {FS => 1, Angle => 1, Vent => 0.3, Size => 5}});

       which draws a broad, large arrow from (0, 1) to (1, 2).

   rect
       Draw a non-rotated rectangle

       Usage: rect ( $x1, $x2, $y1, $y2 )

       Options recognised:

       The following standard options influence this command:

        AXIS, BORDER, COLOUR, FILLTYPE, HATCHING, LINESTYLE,  LINEWIDTH
        JUSTIFY, SCALE, PIX, PITCH, ALIGN

   poly
       Draw a polygon

        Usage: poly ( $x, $y )

       Options recognised:

       The following standard options influence this command:

        AXIS, BORDER, COLOUR, FILLTYPE, HATCHING, LINESTYLE,  LINEWIDTH
        JUSTIFY, SCALE, PIX, PITCH, ALIGN

        # Fill with hatching in two different colours
        $x=sequence(10)/10;
        # First fill with cyan hatching
        poly $x, $x**2, {COLOR=>5, FILL=>3};
        hold;
        # Then do it over again with the hatching offset in phase:
        poly $x, $x**2, {COLOR=>6, FILL=>3, HATCH=>{PHASE=>0.5}};
        release;

   circle
       Plot a circle on the display using the fill setting.

        Usage: circle($x, $y, $radius [, $opt]);

       All arguments can alternatively be given in the options hash using the following options:

       XCenter and YCenter
           The position of the center of the circle

       Radius
           The radius of the circle.

   ellipse
       Plot an ellipse, optionally using fill style.

        Usage: ellipse($x, $y, $a, $b, $theta [, $opt]);

       All arguments can alternatively be given in the options hash using the following options:

       MajorAxis
           The major axis of the ellipse - this must be defined or $a must be given.

       MinorAxis
           The minor axis, like A this is required.

       Theta (synonym Angle)
           The orientation of the ellipse - defaults to 0.0. This is given in radians.

       XCenter and YCenter
           The coordinates of the center of the ellipse. These must be specified or $x and $y
           must be given.

       NPoints
           The number of points used to draw the ellipse. This defaults to 100 and might need
           changing in the case of very large ellipses.

       The routine also recognises the same standard options as accepted by poly.

   rectangle
       Draw a rectangle.

        Usage: rectangle($xcenter, $ycenter, $xside, $yside, [, $angle, $opt]);

       This routine draws a rectangle with the chosen fill style. Internally it calls poly which
       is somewhat slower than "pgrect" but which allows for rotated rectangles as well. The
       routine recognises the same options as "poly" and in addition the following:

       XCenter and YCenter
           The position of the center of the rectangle. XCentre and YCentre are valid synonyms.

       XSide and YSide
           The length of the X and Y sides. If only one is specified the shape is taken to be
           square with that as the side-length, alternatively the user can set Side

       Side
           The length of the sides of the rectangle (in this case a square) - syntactic sugar for
           setting XSide and YSide identical. This is overridden by XSide or YSide if any of
           those are set.

       Angle (synonym Theta)
           The angle at which the rectangle is to be drawn. This defaults to 0.0 and is given in
           radians.

   vect
       Display 2 images as a vector field

        Usage: vect ( $w, $a, $b, [$scale, $pos, $transform, $misval], { opt } );
               $w->vect($a,$b,[$scale,$pos,$transform,$misval], { opt });

       Notes: $transform for image/cont etc. is used in the same way as the "TR()" array in the
       underlying PGPLOT FORTRAN routine but is, fortunately, zero-offset. The transform()
       routine can be used to create this piddle.

       This routine will plot a vector field. $a is the horizontal component and $b the vertical
       component.  The scale factor converts between vector length units and scientific
       positional units.  You can set the scale, position, etc. either by passing in parameters
       in the normal parameter list or by passing in options.

       Options recognised:

            SCALE - Set the scale factor for vector lengths.
              POS - Set the position of vectors.
                    <0 - vector head at coordinate
                    >0 - vector base at coordinate
                    =0 - vector centered on the coordinate
        TRANSFORM - The pixel-to-world coordinate transform vector
          MISSING - Elements with this value are ignored.

       The following standard options influence this command:

        ARROW, ARROWSIZE, AXIS, BORDER, CHARSIZE, COLOUR,
        LINESTYLE, LINEWIDTH,

        $a=rvals(11,11,{Centre=>[5,5]});
        $b=rvals(11,11,{Centre=>[0,0]});
        vect $a, $b, {COLOR=>YELLOW, ARROWSIZE=>0.5, LINESTYLE=>dashed};

   fits_vect
       Display a pair of 2-D piddles as vectors, with FITS header interpretation

        Usage: fits_vect ($a, $b, [$scale, $pos, $transform, $misval] )

       "fits_vect" is to vect as fits_imag is to imag.

   transform
       Create transform array for contour and image plotting

        $win->transform([$xdim,$ydim], $options);

       (For information on coordinate transforms, try PDL::Transform.)  This function creates a
       transform array in the format required by the image and contouring routines. You must call
       it with the dimensions of your image as arguments or pass these as an anonymous hash - see
       the example below.

       Angle
           The rotation angle of the transform, in radians.  Positive numbers rotate the image
           clockwise on the screen.

       ImageDimensions
           The dimensions of the image the transform is required for. The dimensions should be
           passed as a reference to an array.

       Pixinc
           The increment in output coordinate per pixel.

       ImageCenter (or ImageCentre)
           The centre of the image as an anonymous array or as a scalar, in scientific
           coordinates. In the latter case the x and y value for the center will be set equal to
           this scalar. This is particularly useful in the common case when the center is (0, 0).
           (ImageCenter overrides RefPos if both are specified).

       RefPos (or ReferencePosition)
           If you wish to set a pixel other than the image centre to a given value, use this
           option. It should be supplied with a reference to an array containing 2 2-element
           array references, e.g.

            RefPos => [ [ $xpix, $ypix ], [ $xplot, $yplot ] ]

           This will label pixel "($xpix,$ypix)" as being at position "($xplot,$yplot)".  For
           example

            RefPos      => [ [100,74], [ 0, 0 ] ]

           sets the scientific coordinate origin to be at the center of the (100,74) pixel
           coordinate.  The pixel coordinates are pixel-centered, and start counting from 0 (as
           all good pixel coordinates should).

       Example:

          $im = rvals(100, 100);
          $w = PDL::Graphics::PGPLOT::Window->new(Device => '/xs');
          $t = $w->transform(dims($im), {ImageCenter => 0,  Pixinc => 5});
          $w->imag($im, {Transform => $t});

   tline
       Threaded line plotting

        $win->tline($x, $y, $options);

       This is a threaded interface to "line". This is convenient if you have a 2D array and want
       to plot out every line in one go. The routine will apply any options you apply in a
       "reasonable" way. In the sense that it will loop over the options wrapping over if there
       are less options than lines.

       Example:

         $h={Colour => ['Red', '1', 4], Linestyle => ['Solid' ,'Dashed']};
         $tx=zeroes(100,5)->xlinvals(-5,5);
         $ty = $tx + $tx->yvals;
         $win->tline($tx, $ty, $h);

   tpoints
       A threaded interface to points

        Usage: tpoints($x, $y, $options);

       This is a threaded interface to "points". This is convenient if you have a 2D array and
       want to plot out every line in one go. The routine will apply any options you apply in a
       "reasonable" way. In the sense that it will loop over the options wrapping over if there
       are less options than lines.

       Example:

         $h={Colour => ['Red', '1', 4], Linestyle => ['Solid' ,'Dashed']};
         $tx=zeroes(100,5)->xlinvals(-5,5);
         $ty = $tx + $tx->yvals;
         tpoints($tx, $ty, $h);

   tcircle
       A threaded interface to circle

        Usage: tcircle($x, $y, $r, $options);

       This is a threaded interface to "circle". This is convenient if you have a list of circle
       centers and radii and want to draw every circle in one go.  The routine will apply any
       options you apply in a "reasonable" way, in the sense that it will loop over the options
       wrapping over if there are less options than circles.

       Example:

        $x=sequence(5);
        $y=random(5);
        $r=sequence(5)/10 + 0.1;
        $h={justify => 1,Color => ['red','green','blue'], filltype => ['solid','outline','hatched','cross_hatched']};
        tcircle($x, $y, $r, $h);

       Note that $x and $y must be the same size (>1D is OK, though meaningless as far as
       "tcircle" is concerned). $r can be the same size as $x OR a 1-element piddle OR a single
       perl scalar.

   Text routines
   text
       Write text in a plot window at a specified position.

        Usage: text ($text, $x, $y [, $opt])

       Options recognised:

       "ANGLE"
           The angle in degrees between the baseline of the text and the horisontal (increasing
           counter-clockwise). This defaults to 0.

       "JUSTIFICATION"
           The justification of the text relative to the position specified. It defaults to 0.0
           which gives left-justified text. A value of 0.5 gives centered text and a value of 1.0
           gives right-justified text.

       "XPos", "YPos", "Text"
           These gives alternative ways to specify the text and position.

       "BackgroundColour"
           This sets the background colour for the text in case an opaque background is desired.
           You can also use the synonyms "Bg" and "BackgroundColor".

       The following standard options influence this command:

          COLOUR, CHARSIZE

         line sequence(10), sequence(10)**2;
         text 'A parabola', 3, 9, {Justification => 1, Angle=>atan2(6,1)};

   legend
       Add a legend to a plot

        Usage: legend($text, $x, $y, [, $width], $opt]);

       This function adds a legend to an existing plot. The action is primarily controlled by
       information in the options hash, and the basic idea is that $x and $y determines the upper
       left hand corner of the box in which the legend goes. If the width is specified either as
       an argument or as an option in the option hash this is used to determine the optimal
       character size to fit the text into part of this width (defaults to 0.5 - see the
       description of "TextFraction" below). The rest of the width is filled out with either
       lines or symbols according to the content of the "LineStyle", "Symbol", "Colour" and
       "LineWidth" options.

       The local options recognised are as follows:

       "Text"
           An anonymous array of annotations, can also be specified directly.

       "XPos" and "YPos"
           The X and Y position of the upper left-hand corner of the text.

       "Width" and "Height"
           The width and/or height of each line (including symbol/line). This is used to
           determine the character size. If any of these are set to 'Automatic' the current
           character size will be used.

       "TextFraction"
           The text and the symbol/line is set inside a box. "TextFraction" determines how much
           of this box should be devoted to text. This defaults to 0.5. You can also use
           "Fraction" as a synonym to this.

       "TextShift"
           This option allows for fine control of the spacing between the text and the start of
           the line/symbol. It is given in fractions of the total width of the legend box. The
           default value is 0.1.

       "VertSpace" or "VSpace"
           By default the text lines are separated by one character height (in the sense that if
           the separation were 0 then they would lie on top of each other). The "VertSpace"
           option allows you to increase (or decrease) this gap in units of the character height;
           a value of 0.5 would add half a character height to the gap between lines, and -0.5
           would remove the same distance.  The default value is 0.

       "BackgroundColour"
           This sets the background colour for the text in case an opaque background is desired.
           You can also use the synonyms "Bg" and "BackgroundColor".

         line $x, $y, {Color => 'Red', LineStyle => 'Solid'};
         line $x2, $y2, {Color => 'Blue', 'LineStyle' => 'Dashed', LineWidth => 10};

         legend ['A red line', 'A blue line'], 5, 5,
             {LineStyle => ['Solid', 'Dashed'], Colour => ['Red', 'Blue']
              LineWidth => [undef, 10]}; # undef gives default.

   Cursor routines
   cursor
       Interactively read cursor positions.

        Usage: ($x, $y, $ch, $xref, $yref) = cursor($opt)

       This routine has no standard input parameters, but the type of cursor can be set by
       setting the option "Type" as a key in the anonymous hash $opt. The first three return
       values from the function are always defined and gives the position selected by the user
       and the character pressed.

       Depending on the cursor type selected the last two arguments might also be defined and
       these give a reference position. For instance if the cursor is selected to be "Rectangle"
       then the reference position gives one of the corners of the rectangle and $x and $y the
       diagonally opposite one.

       Options recognised:

       XRef, YRef
           The reference position to be used

       Type
           The type of cursor. This can be selected using a number between 0 and 7 as in PGPLOT,
           or alternatively you can specify these as, "Default" (0), "RadialLine" (1),
           "Rectangle" (2), "TwoHorizontalLines" (3), "TwoVerticalLines" (4), "HorizontalLine"
           (5), "VerticalLine" (6) and "CrossHair" (7) respectively. The default cursor is just
           the normal mouse cursor.

           For the "RadialLine" you must specify the reference point, whereas for the
           "Two(Vertical|Horizontal)Lines" cursor the X or Y reference point, respectively, must
           be specified.

       To select a region on a plot, use the rectangle cursor:

         ($x, $y, $ch, $xref, $yref) = cursor({Type => 'Rectangle'});
         poly pdl($x, $xref, $xref, $x, $x), pdl($y, $y, $yref, $yref, $y);

       To select a region of the X-axis:

         ($x1, $y1, $ch) = cursor({Type => 'VerticalLine'});
         ($x2, $y2, $ch) = cursor({Type => 'TwoVerticalLines', XRef => $x1});

Internal routines

   signal_catcher, catch_signals, release_signals
       To prevent pgplot from doing a fandango on core, we have to block interrupts during PGPLOT
       calls.  Specifically, INT needs to get caught.  These internal routines provide a
       mechanism for that.

       You simply bracket any PGPLOT calls with &catch_signals above and &release_signals below,
       and the signal_catcher will queue up any signals (like INT -- the control-C interrupt)
       until the &release_signals call.

       Any exit path from your hot code must include &release_signals, or interrupts could be
       deferred indefinitely (which would be a bug).  This includes calls to &barf -- even barfs
       from someone you called!  So avoid calling out of the local module if possible, and use
       release_and_barf() instead of barf() from within this module.

       Perl 5.6.1 interrupt handling has a bug that this code tickles -- sometimes the re-emitted
       signals vanish into hyperspace.  Perl 5.8 seems NOT to have that problem.

   _open_new_window
       Open a new window. This sets the window ID, which is the one used when accessing a window
       later using "pgslct". It also sets the window name to something easily remembered if it
       has not been set before.

   _setup_window
       This routine sets up a new window with its shape and size. This is also where the size
       options are actually parsed. These are then forgotten (well, they are stored in
       $self->{Options}) and the corresponding aspect ratio and window width is stored.  See the
       discussion under new() for the logic.

       Finally the subpanels are set up using "pgsubp" and colours and linewidth are adjusted
       according to whether we have a hardcopy device or not.

   _status
       This routine checks PGPLOT's status for the window. It returns OPEN if the window is open
       and CLOSED if it is closed.  (Windows can be closed but still exist).

   _reopen
       This functions reopens a window. Since this is an internal function it does not have a lot
       of error-checking. Make sure the device is closed before calling this routine.

       There is an unfortunate problem which pops up viz. that the window name cannot be changed
       at this point since we are offering that to the rest of the world. That might be sensible,
       but it means that the window name will not reflect the id of the window - use "id()" for
       that (this is also why we do not call "open_new_window" )

   _advance_panel
       This routine advances one plot panel, updating the CurrentPanel as well.  If the advance
       will proceed past the page the page will be erased. Also note that when you advance one
       panel the hold value will be changed.

   _check_move_or_erase
       This routine is a utility routine which checks if we need to move panel, and if so will do
       this. It also checks if it is necessary to advance panels, and whether they need to be
       erased.

   _thread_options
       This function is a cludgy utility function that expands an options hash to an array of
       hashes looping over options. This is mainly of use for "threaded" interfaces to standard
       plotting routines.

   options
       Access the options used when originally opening the window. At the moment this is not
       updated when the window is changed later.

   id
       Access the window ID that PGPLOT uses for the present window.

   device
       This function returns the device type of the present window.

   name
       Accessor to set and examine the name of a window.

   focus
       Set focus for subsequent PGPLOT commands to this window.

   info
       Get general information about the PGPLOT environment.

        @ans = $self->info( @item );

       The valid values of @item are as below, where case is not important:

         VERSION     - What PGPLOT version is in use.
         STATE       - The status of the output device, this is returns 'OPEN'.
                       if the device is open and 'CLOSED' otherwise.
         USER        - The username of the owner of the spawning program.
         NOW         - The current date and time in the format
                       'dd-MMM-yyyy hh:mm'. Most people are likely to use Perl
                       functions instead.
         DEVICE    * - The current PGPLOT device or file, see also device().
         FILE      * - The filename for the current device.
         TYPE      * - And the device type for the current device.
         DEV/TYPE  * - This combines DEVICE and TYPE in a form that can be used
                       as input to new.
         HARDCOPY  * - This is flag which is set to 'YES' if the current device is
                       a hardcopy device and 'NO' otherwise.
         TERMINAL  * - This flag is set to 'YES' if the current device is the
                       user's terminal and 'NO' otherwise.
         CURSOR    * - A flag ('YES' or 'NO') to inform whether the current device
                       has a cursor.

       Those items marced with a "*" only return a valid answer if the window is open.  A
       question mark ("?") is returned if the item is not recognised or the information is not
       available.

   _extract_hash
       This routine takes and array and returns the first hash reference found as well as those
       elements that are not hashes. Note the latter point because all other references to hashes
       in the array will be lost.

   _parse_unit
       Convert a unit string or number into a PGPLOT-certified length unit specification, or
       return undef if it won't go.

   _parse_options
       This is a convenience routine for parsing a set of options. It returns both the full set
       of options and those that the user has set.

   _save_status
       Saves the PGPLOT state so that changes to settings can be made and then the present state
       restored by "_restore_status".

   _restore_status
       Restore the PGPLOT state. See "_save_status".

   _checkarg
       This routine checks and optionally alters the arguments given to it.

   _set_colour
       This is an internal routine that encapsulates all the nastiness of setting colours
       depending on the different PGPLOT colour models (although HLS is not supported).

       The routine works in the following way:

       ·       At initialisation of the plot device the work colour index is set to 16. The work
               index is the index the routine will modify unless the user has specified something
               else.

       ·       The routine should be used after standard interpretation and synonym matching has
               been used. So if the colour is given as input is an integer that colour index is
               used.

       ·       If the colour is a reference the routine checks whether it is an "ARRAY" or a
               "PDL" reference. If it is not an error message is given.  If it is a "PDL"
               reference it will be converted to an array ref.

       ·       If the array has four elements the first element is interpreted as the colour
               index to modify and this overrules the setting for the work index used internally.
               Otherwise the work index is used and incremented until the maximum number of
               colours for the output device is reached (as indicated by "pgqcol"). Should you
               wish to change that you need to read the PGPLOT documentation - it is somewhat
               device dependent.

       ·       When the array has been recognised the R,G and B colours of the user-set index or
               work index is set using the "pgscr" command and we are finished.

       ·       If the input colour instead is a string we try to set the colour using the PGPLOT
               routine "pgscrn" with no other error-checking. This should be ok,  as that routine
               returns a rather sensible error-message.

   _standard_options_parser
       This internal routine is the default routine for parsing options. This routine deals with
       a subset of options that most routines will accept.

   _image_xyrange
       Given a PGPLOT tr matrix and an image size, calculate the data world coordinates over
       which the image ranges.  This is used in imag and cont.  It keeps track of the required
       half-pixel offset to display images properly -- eg feeding in no tr matrix at all, nx=20,
       and ny=20 will will return (-0.5,19.5,-0.5,19.5).  It also checks the options hash for
       XRange/YRange specifications and, if they are present, it overrides the appropriate output
       with the exact ranges in those fields.

   _FITS_tr
       Given a FITS image, return the PGPLOT transformation matrix to convert pixel coordinates
       to scientific coordinates.   Used by fits_imag, fits_rgbi, and fits_cont, but may come in
       handy for other methods.

         my $tr = _FITS_tr( $win, $img );
         my $tr = _FITS_tr( $win, $img, $opts );

       The return value ($tr in the examples above) is the same as returned by the transform()
       routine, with values set up to convert the pixel to scientific coordinate values for the
       two-dimensional image $img. The $opts argument is optional and should be a HASH reference;
       currently it only understands one key (any others are ignored):

         WCS => undef (default), "", or "A" to "Z"

       Both the key name and value are case insensitive. If left as "undef" or "" then the
       primary coordinate mapping from the header is used, otherwise use the additional WCS
       mapping given by the appropriate letter.  We make no checks that the given mapping is
       available; the routine falls back to the unit mapping if the specified system is not
       available.

       The WCS option has only been tested on images from the Chandra X-ray satellite
       (<http://chandra.harvard.edu/>) created by the CIAO software package
       (<http://cxc.harvard.edu/ciao/>), for which you should set "WCS => "P"" to use the
       "PHYSICAL" coordinate system.

       See <http://fits.cv.nrao.edu/documents/wcs/wcs.html> for further information on the
       Representation of World Coordinate Systems in FITS.

INTERNAL

       The coding tries to follow reasonable standards, so that all functions starting with an
       underscore should be considered as internal and should not be called from outside the
       package. In addition most routines have a set of options. These are encapsulated and are
       not accessible outside the routine. This is to avoid collisions between different
       variables.

AUTHOR

       Karl Glazebrook [kgb@aaoepp.aao.gov.au] modified by Jarle Brinchmann
       (jarle@astro.ox.ac.uk) who is also responsible for the OO interface, docs mangled by
       Tuomas J. Lukka (lukka@fas.harvard.edu) and Christian Soeller (c.soeller@auckland.ac.nz).
       Further contributions and bugfixes from Kaj Wiik, Doug Burke, Craig DeForest, and many
       others.

       All rights reserved. There is no warranty. You are allowed to redistribute this software /
       documentation under certain conditions. For details, see the file COPYING in the PDL
       distribution. If this file is separated from the PDL distribution, the copyright notice
       should be included in the file.