Provided by: libimager-perl_1.004+dfsg-1build1_amd64 
NAME
Imager::Draw - Draw primitives to images
SYNOPSIS
use Imager;
use Imager::Fill;
$img = ...;
$blue = Imager::Color->new( 0, 0, 255 );
$fill = Imager::Fill->new(hatch=>'stipple');
$img->line(color=>$blue, x1=>10, x2=>100,
y1=>20, y2=>50, aa=>1, endp=>1 );
$img->polyline(points=>[[$x0,$y0], [$x1,$y1], [$x2,$y2]],
color=>$blue);
$img->polyline(x=>[$x0,$x1,$x2], y=>[$y0,$y1,$y2], aa=>1);
$img->box(color=> $blue, xmin=> 10, ymin=>30,
xmax=>200, ymax=>300, filled=>1);
$img->box(fill=>$fill);
$img->arc(color=>$blue, r=>20, x=>200, y=>100,
d1=>10, d2=>20 );
$img->circle(color=>$blue, r=>50, x=>200, y=>100);
$img->polygon(points=>[[$x0,$y0], [$x1,$y1], [$x2,$y2]],
color=>$blue);
$img->polygon(x=>[$x0,$x1,$x2], y=>[$y0,$y1,$y2]);
$img->flood_fill(x=>50, y=>50, color=>$color);
$img->setpixel(x=>50, y=>70, color=>$color);
$img->setpixel(x=>[ 50, 60, 70 ], y=>[20, 30, 40], color=>$color);
my $color = $img->getpixel(x=>50, y=>70);
my @colors = $img->getpixel(x=>[ 50, 60, 70 ], y=>[20, 30, 40]);
# drawing text
my $font = Imager::Font->new(...) or die;
$img->string(x => 50, y => 70,
font => $font,
string => "Hello, World!",
color => 'red',
size => 30,
aa => 1);
# bottom right-hand corner of the image
$img->align_string(x => $img->getwidth() - 1,
y => $img->getheight() - 1,
halign => 'right',
valign => 'bottom',
string => 'Imager',
font => $font,
size => 12);
# low-level functions
my @colors = $img->getscanline(y=>50, x=>10, width=>20);
$img->setscanline(y=>60, x=>20, pixels=>\@colors);
my @samples = $img->getsamples(y=>50, x=>10, width=>20,
channels=>[ 2, 0 ]);
DESCRIPTION
It is possible to draw with graphics primitives onto images. Such primitives include
boxes, arcs, circles, polygons and lines. The coordinate system in Imager has the origin
"(0,0)" in the upper left corner of an image with co-ordinates increasing to the right and
bottom. For non anti-aliasing operation all coordinates are rounded towards the nearest
integer. For anti-aliased operations floating point coordinates are used.
Drawing is assumed to take place in a coordinate system of infinite resolution. This is
the typical convention and really only matters when it is necessary to check for off-by-
one cases. Typically it's useful to think of "(10, 20)" as "(10.00, 20.00)" and consider
the consequences.
Color Parameters
The "color" parameter for any of the drawing methods can be an Imager::Color object, a
simple scalar that Imager::Color can understand, a hashref of parameters that
Imager::Color->new understands, or an arrayref of red, green, blue values, for example:
$image->box(..., color=>'red');
$image->line(..., color=>'#FF0000');
$image->flood_fill(..., color=>[ 255, 0, 255 ]);
While supplying colors as names, array references or CSS color specifiers is convenient,
for maximum performance you should supply the color as an Imager::Color object:
my @colors = map Imager::Color->new($_), qw/red green blue/
for my $i (1..1000) {
$image->box(..., color => $colors[rand @colors]);
}
Fill Parameters
All filled primitives, i.e. "arc()", "box()", "circle()", "polygon()" and the
"flood_fill()" method can take a "fill" parameter instead of a "color" parameter which can
either be an Imager::Fill object, or a reference to a hash containing the parameters used
to create the fill, for example:
$image->box(..., fill=>{ hatch => 'check1x1' });
my $fillimage = Imager->new;
$fillimage->read(file=>$somefile) or die;
$image->flood_fill(..., fill=>{ image=>$fillimage });
Currently you can create opaque or transparent plain color fills, hatched fills, image
based fills and fountain fills. See Imager::Fill for more information.
Polygon Fill Modes
When filling a polygon that overlaps itself, or when filling several polygons with
polypolygon() that overlap each other, you can supply a "mode" parameter that controls how
the overlap is resolved. This can have one of two possible values:
• "evenodd" - if areas overlap an odd number of times, they are filled, and are
otherwise unfilled. This is the default and the historical Imager polygon fill mode.
• "nonzero" - areas that have an unbalanced clockwise and anti-clockwise boundary are
filled. This is the same as "WindingRule" for X and "WINDING" for Win32 GDI.
"nonzero" allows polygons to overlap, either with itself, or with another polygon in the
same polypolygon() call, without producing unfilled area in the overlap, and also allows
areas to be cut out of the area by specifying the points making up a cut-out in the
opposite order.
List of primitives
line()
$img->line(color=>$green, x1=>10, x2=>100,
y1=>20, y2=>50, aa=>1, endp=>1 );
Draws a line from (x1,y1) to (x2,y2). The endpoint (x2,y2) is drawn by default. If
"endp" of 0 is specified then the endpoint will not be drawn. If "aa" is set then the
line will be drawn anti-aliased. The "antialias" parameter is still available for
backwards compatibility.
Parameters:
• "x1", "y1" - starting point of the line. Required.
• "x2", "y2" - end point of the line. Required.
• "color" - the color of the line. See "Color Parameters". Default: black.
• "endp" - if zero the end point of the line is not drawn. Default: 1 - the end
point is drawn. This is useful to set to 0 when drawing a series of connected
lines.
• "aa" - if true the line is drawn anti-aliased. Default: 0.
polyline()
$img->polyline(points=>[[$x0,$y0],[$x1,$y1],[$x2,$y2]],color=>$red);
$img->polyline(x=>[$x0,$x1,$x2], y=>[$y0,$y1,$y2], aa=>1);
"polyline" is used to draw multiple lines between a series of points. The point set
can either be specified as an arrayref to an array of array references (where each
such array represents a point). The other way is to specify two array references.
The "antialias" parameter is still available for backwards compatibility.
• points - a reference to an array of references to arrays containing the co-
ordinates of the points in the line, for example:
my @points = ( [ 0, 0 ], [ 100, 0 ], [ 100, 100 ], [ 0, 100 ] );
$img->polyline(points => \@points);
• x, y - each is an array of x or y ordinates. This is an alternative to supplying
the "points" parameter.
# same as the above points example
my @x = ( 0, 100, 100, 0 );
my @y = ( 0, 0, 100, 100 );
$img->polyline(x => \@x, y => \@y);
• "color" - the color of the line. See "Color Parameters". Default: black.
• "aa" - if true the line is drawn anti-aliased. Default: 0. Can also be supplied
as "antialias" for backward compatibility.
box()
$blue = Imager::Color->new( 0, 0, 255 );
$img->box(color => $blue, xmin=>10, ymin=>30, xmax=>200, ymax=>300,
filled=>1);
If any of the edges of the box are omitted it will snap to the outer edge of the image
in that direction. If "filled" is omitted the box is drawn as an outline. Instead of
a color it is possible to use a "fill" pattern:
$fill = Imager::Fill->new(hatch=>'stipple');
$img->box(fill=>$fill); # fill entire image with a given fill pattern
$img->box(xmin=>10, ymin=>30, xmax=>150, ymax=>60,
fill => { hatch=>'cross2' });
Also if a color is omitted a color with (255,255,255,255) is used instead. [NOTE:
This may change to use "$img->fgcolor()" in the future].
Box does not support fractional coordinates yet.
Parameters:
• "xmin" - left side of the box. Default: 0 (left edge of the image)
• "ymin" - top side of the box. Default: 0 (top edge of the image)
• "xmax" - right side of the box. Default: "$img->getwidth-1". (right edge of the
image)
• "ymax" - bottom side of the box. Default: "$img->getheight-1". (bottom edge of
the image)
Note: "xmax" and "ymax" are inclusive - the number of pixels drawn for a filled
box is "(xmax-xmin+1) * (ymax-ymin+1)".
• "box" - a reference to an array of (left, top, right, bottom) co-ordinates. This
is an alternative to supplying "xmin", "ymin", "xmax", "ymax" and overrides their
values.
• "color" - the color of the line. See "Color Parameters". Default: white. This
is ignored if the filled parameter
• "filled" - if non-zero the box is filled with color instead of outlined. Default:
an outline is drawn.
• "fill" - the fill for the box. If this is supplied then the box will be filled.
See "Fill Parameters".
arc()
$img->arc(color=>$red, r=>20, x=>200, y=>100, d1=>10, d2=>20 );
This creates a filled red arc with a 'center' at (200, 100) and spans 10 degrees and
the slice has a radius of 20.
It's also possible to supply a "fill" parameter.
To draw just an arc outline - just the curve, not the radius lines, set filled to 0:
Parameters:
$img->arc(color=>$red, r=>20, x=>200, y=>100, d1=>10, d2=>20, filled=>0 );
• "x", "y" - center of the filled arc. Default: center of the image.
• "r" - radius of the arc. Default: 1/3 of min(image height, image width).
• "d1" - starting angle of the arc, in degrees. Default: 0
• "d2" - ending angle of the arc, in degrees. Default: 361.
• "color" - the color of the filled arc. See "Color Parameters". Default: white.
Overridden by "fill".
• "fill" - the fill for the filled arc. See "Fill Parameters"
• "aa" - if true the filled arc is drawn anti-aliased. Default: false.
Anti-aliased arc() is experimental for now, I'm not entirely happy with the
results in some cases.
• "filled" - set to 0 to draw only an outline.
# arc going through angle zero:
$img->arc(d1=>320, d2=>40, x=>100, y=>100, r=>50, color=>'blue');
# complex fill arc
$img->arc(d1=>135, d2=>45, x=>100, y=>150, r=>50,
fill=>{ solid=>'red', combine=>'diff' });
# draw an anti-aliased circle outline
$img->arc(x => 100, y => 150, r => 150, filled => 0,
color => '#F00', aa => 1);
# draw an anti-aliased arc
$img->arc(x => 100, y => 150, r => 90, filled => 0,
color => '#0f0', aa => 1, d1 => 90, d2 => 180);
circle()
$img->circle(color=>$green, r=>50, x=>200, y=>100, aa=>1, filled=>1);
This creates an anti-aliased green circle with its center at (200, 100) and has a
radius of 50. It's also possible to supply a "fill" parameter instead of a color
parameter.
$img->circle(r => 50, x=> 150, y => 150, fill=>{ hatch => 'stipple' });
To draw a circular outline, set "filled" to 0:
$img->circle(color=>$green, r=>50, x=>200, y=>100, aa=>1, filled=>0);
• "x", "y" - center of the filled circle. Default: center of the image.
• "r" - radius of the circle. Default: 1/3 of min(image height, image width).
• "color" - the color of the filled circle. See "Color Parameters". Default:
white. Overridden by "fill".
• "fill" - the fill for the filled circle. See "Fill Parameters"
• "aa" - if true the filled circle is drawn anti-aliased. Default: false.
• "filled" - set to 0 to just draw an outline.
polygon()
$img->polygon(points=>[[$x0,$y0],[$x1,$y1],[$x2,$y2]],color=>$red);
$img->polygon(x=>[$x0,$x1,$x2], y=>[$y0,$y1,$y2], fill=>$fill);
Polygon is used to draw a filled polygon. Currently the polygon is always drawn anti-
aliased, although that will change in the future. Like other anti-aliased drawing
functions its coordinates can be specified with floating point values. As with other
filled shapes it's possible to use a "fill" instead of a color.
• "points" - a reference to an array of references to arrays containing the co-
ordinates of the points in the line, for example:
my @points = ( [ 0, 0 ], [ 100, 0 ], [ 100, 100 ], [ 0, 100 ] );
$img->polygon(points => \@points);
• "x", "y" - each is an array of x or y ordinates. This is an alternative to
supplying the "points" parameter.
# same as the above points example
my @x = ( 0, 100, 100, 0 );
my @y = ( 0, 0, 100, 100 );
$img->polygon(x => \@x, y => \@y);
• "color" - the color of the filled polygon. See "Color Parameters". Default:
black. Overridden by "fill".
• "fill" - the fill for the filled circle. See "Fill Parameters"
• "mode" - fill mode for the polygon. See "Polygon Fill Modes"
Note: the points specified are as offsets from the top-left of the image, not as pixel
locations. This means that:
$img->polygon(points => [ [ 0, 0 ], [ 1, 0 ], [ 1, 1 ], [ 0, 1 ] ]);
fills only a single pixel at "(0, 0)", not four.
polypolygon()
$img->polypolygon(points => $points, color => $color);
Draw multiple polygons, either filled or unfilled.
• "points" - is an array reference containing polygon definitions, each polygon
definition is a reference to an array containing two arrays, one each for the "x"
and "y" co-ordinates.
• "filled" - if true, fill the polygons with the color defined by "color".
• "color" - the color to draw the polygons with if "fill" is not supplied.
• "fill" - fill the polygons with this fill if supplied.
• "mode" - fill mode for the polygon. See "Polygon Fill Modes"
Note: the points specified are as offsets from the top-left of the image, not as pixel
locations. This means that:
$img->polypolygon(points => [ [ [ 0, 1, 1, 0 ], [ 0, 0, 1, 1 ] ] ],
filled => 1);
fills only a single pixel at "(0, 0)", not four.
flood_fill()
You can fill a region that all has the same color using the flood_fill() method, for
example:
$img->flood_fill(x=>50, y=>50, color=>$color);
will fill all regions the same color connected to the point (50, 50).
Alternatively you can fill a region limited by a given border color:
# stop at the red border
$im->flood_fill(x=>50, y=>50, color=>$color, border=>"red");
You can also fill with a complex fill:
$img->flood_fill(x=>50, y=>50, fill=>{ hatch=>'cross1x1' });
Parameters:
• "x", "y" - the start point of the fill.
• "color" - the color of the filled area. See "Color Parameters". Default: white.
Overridden by "fill".
• "fill" - the fill for the filled area. See "Fill Parameters"
• "border" - the border color of the region to be filled. If this parameter is
supplied flood_fill() will stop when it finds this color. If this is not supplied
then a normal fill is done. "border" can be supplied as a "Color Parameters".
setpixel()
$img->setpixel(x=>50, y=>70, color=>$color);
$img->setpixel(x=>[ 50, 60, 70 ], y=>[20, 30, 40], color=>$color);
setpixel() is used to set one or more individual pixels.
You can supply a single set of co-ordinates as scalar "x" and "y" parameters, or set
either to an arrayref of ordinates.
If one array is shorter than another the final value in the shorter will be duplicated
until they match in length.
If only one of "x" or "y" is an array reference then setpixel() will behave as if the
non-reference value were an array reference containing only that value.
eg.
my $count = $img->setpixel(x => 1, y => [ 0 .. 3 ], color => $color);
behaves like:
my $count = $img->setpixel(x => [ 1 ], y => [ 0 .. 3 ], color => $color);
and since the final element in the shorter array is duplicated, this behaves like:
my $count = $img->setpixel(x => [ 1, 1, 1, 1 ], y => [ 0 .. 3 ],
color => $color);
Parameters:
• x, y - either integers giving the co-ordinates of the pixel to set or array
references containing a set of pixels to be set.
• color - the color of the pixels drawn. See "Color Parameters". Default: white.
Returns the number of pixels drawn, if no pixels were drawn, but none of the errors
below occur, returns "0 but true".
For other errors, setpixel() returns an empty list and sets errstr().
Possible errors conditions include:
• the image supplied is empty
• a reference to an empty array was supplied for "x" or "y"
• "x" or "y" wasn't supplied
• "color" isn't a valid color, and can't be converted to a color.
getpixel()
my $color = $img->getpixel(x=>50, y=>70); my @colors =
$img->getpixel(x=>[ 50, 60, 70 ], y=>[20, 30, 40]); my $colors_ref =
$img->getpixel(x=>[ 50, 60, 70 ], y=>[20, 30, 40]);
getpixel() is used to retrieve one or more individual pixels.
You can supply a single set of co-ordinates as scalar "x" and "y" parameters, or set
each to an arrayref of ordinates.
If one array is shorter than another the final value in the shorter will be duplicated
until they match in length.
If only one of "x" or "y" is an array reference then getpixel() will behave as if the
non-reference value were an array reference containing only that value.
eg.
my @colors = $img->getpixel(x => 0, y => [ 0 .. 3 ]);
behaves like:
my @colors = $img->getpixel(x => [ 0 ], y => [ 0 .. 3 ]);
and since the final element in the shorter array is duplicated, this behaves like:
my @colors = $img->getpixel(x => [ 0, 0, 0, 0 ], y => [ 0 .. 3 ]);
To receive floating point colors from getpixel(), set the "type" parameter to 'float'.
Parameters:
• "x", "y" - either integers giving the co-ordinates of the pixel to set or array
references containing a set of pixels to be set.
• "type" - the type of color object to return, either '8bit' for Imager::Color
objects or 'float' for Imager::Color::Float objects. Default: '8bit'.
When called with an array reference for either or "x" or "y", getpixel() will return a
list of colors in list context, and an arrayref in scalar context.
If a supplied co-ordinate is outside the image then "undef" is returned for the pixel.
Each color is returned as an Imager::Color object or as an Imager::Color::Float object
if "type" is set to "float".
Possible errors conditions include:
• the image supplied is empty
• a reference to an empty array was supplied for "x" or "y"
• "x" or "y" wasn't supplied
• "type" isn't a valid value.
For any of these errors getpixel() returns an empty list.
string()
my $font = Imager::Font->new(file=>"foo.ttf");
$img->string(x => 50, y => 70,
string => "Hello, World!",
font => $font,
size => 30,
aa => 1,
color => 'white');
Draws text on the image.
Parameters:
• "x", "y" - the point to draw the text from. If "align" is 0 this is the top left
of the string. If "align" is 1 (the default) then this is the left of the string
on the baseline. Required.
• "string" - the text to draw. Required unless you supply the "text" parameter.
• "font" - an Imager::Font object representing the font to draw the text with.
Required.
• "aa" - if non-zero the output will be anti-aliased. Default: the value set in
Imager::Font->new() or 0 if not set.
• "align" - if non-zero the point supplied in (x,y) will be on the base-line, if
zero then (x,y) will be at the top-left of the string.
i.e. if drawing the string "yA" and align is 0 the point (x,y) will aligned with
the top of the A. If align is 1 (the default) it will be aligned with the
baseline of the font, typically bottom of the A, depending on the font used.
Default: the value set in Imager::Font->new, or 1 if not set.
• "channel" - if present, the text will be written to the specified channel of the
image and the color parameter will be ignore.
• "color" - the color to draw the text in. Default: the color supplied to
Imager::Font->new, or red if none.
• "size" - the point size to draw the text at. Default: the size supplied to
Imager::Font->new, or 15.
• "sizew" - the width scaling to draw the text at. Default: the value of "size".
• "utf8" - for drivers that support it, treat the string as UTF-8 encoded. For
versions of perl that support Unicode (5.6 and later), this will be enabled
automatically if the "string" parameter is already a UTF-8 string. See "UTF-8" in
Imager::Font for more information.
• "vlayout" - for drivers that support it, draw the text vertically. Note: I
haven't found a font that has the appropriate metrics yet.
• "text" - alias for the "string" parameter.
On error, string() returns false and you can use $img->errstr to get the reason for
the error.
align_string()
Draws text aligned around a point on the image.
# "Hello" centered at 100, 100 in the image.
my ($left, $top, $right, $bottom) =
$img->align_string(string=>"Hello",
x=>100, y=>100,
halign=>'center', valign=>'center',
font=>$font);
Parameters:
• "x", "y" - the point to draw the text from. If "align" is 0 this is the top left
of the string. If "align" is 1 (the default) then this is the left of the string
on the baseline. Required.
• "string" - the text to draw. Required unless you supply the "text" parameter.
• "font" - an Imager::Font object representing the font to draw the text with.
Required.
• "aa" - if non-zero the output will be anti-aliased
• "valign" - vertical alignment of the text against (x,y)
• "top" - Point is at the top of the text.
• "bottom" - Point is at the bottom of the text.
• "baseline" - Point is on the baseline of the text. This is the default.
• "center" - Point is vertically centered within the text.
• "halign" - horizontal alignment of the text against (x,y)
• "left" - The point is at the left of the text. This is the default.
• "start" - The point is at the start point of the text.
• "center" - The point is horizontally centered within the text.
• "right" - The point is at the right end of the text.
• "end" - The point is at the end point of the text.
• "channel" - if present, the text will be written to the specified channel of the
image and the color parameter will be ignore.
• "color" - the color to draw the text in. Default: the color supplied to
Imager::Font->new, or red if none.
• "size" - the point size to draw the text at. Default: the size supplied to
Imager::Font->new, or 15.
• "sizew" - the width scaling to draw the text at. Default: the value of "size".
• "utf8" - for drivers that support it, treat the string as UTF-8 encoded. For
versions of perl that support Unicode (5.6 and later), this will be enabled
automatically if the "string" parameter is already a UTF-8 string. See "UTF-8" in
Imager::Font for more information.
• "vlayout" - for drivers that support it, draw the text vertically. Note: I
haven't found a font that has the appropriate metrics yet.
• "text" - alias for the "string" parameter.
On success returns a list of bounds of the drawn text, in the order left, top, right,
bottom.
On error, align_string() returns an empty list and you can use "$img->errstr" to get
the reason for the error.
setscanline()
Set all or part of a horizontal line of pixels to an image. This method is most
useful in conjunction with "getscanline()".
The parameters you can pass are:
• "y" - vertical position of the scan line. This parameter is required.
• "x" - position to start on the scan line. Default: 0
• "pixels" - either a reference to an array containing Imager::Color objects, an
reference to an array containing Imager::Color::Float objects or a scalar
containing packed color data.
If "type" is "index" then this can either be a reference to an array of palette
color indexes or a scalar containing packed indexes.
See "Packed Color Data" for information on the format of packed color data.
• "type" - the type of pixel data supplied. If you supply an array reference then
this is determined automatically. If you supply packed color data this defaults
to '8bit', if your data is packed floating point color data then you need to set
this to 'float'.
You can use "float" or "8bit" samples with any image.
If this is "index" then "pixels" should be either an array of palette color
indexes or a packed string of color indexes.
Returns the number of pixels set.
Each of the following sets 5 pixels from (5, 10) through (9, 10) to blue, red, blue,
red, blue:
my $red_color = Imager::Color->new(255, 0, 0);
my $blue_color = Imager::Color->new(0, 0, 255);
$image->setscanline(y=>10, x=>5, pixels=>
[ ($blue_color, $red_color) x 2, $blue_color ]);
# use floating point color instead, for 16-bit plus images
my $red_colorf = Imager::Color::Float->new(1.0, 0, 0);
my $blue_colorf = Imager::Color::Float->new(0, 0, 1.0);
$image->setscanline(y=>10, x=>5, pixels=>
[ ($blue_colorf, $red_colorf) x 2, $blue_colorf ]);
# packed 8-bit data
$image->setscanline(y=>10, x=>5, pixels=>
pack("C*", ((0, 0, 255, 255), (255, 0, 0, 255)) x 2,
(0, 0, 255, 255)));
# packed floating point samples
$image->setscanline(y=>10, x=>5, type=>'float', pixels=>
pack("d*", ((0, 0, 1.0, 1.0), (1.0, 0, 0, 1.0)) x 2,
(0, 0, 1.0, 1.0)));
Copy even rows from one image to another:
for (my $y = 0; $y < $im2->getheight; $y+=2) {
$im1->setscanline(y=>$y,
pixels=>scalar($im2->getscanline(y=>$y)));
}
Set the blue channel to 0 for all pixels in an image. This could be done with convert
too:
for my $y (0..$im->getheight-1) {
my $row = $im->getscanline(y=>$y);
$row =~ s/(..).(.)/$1\0$2/gs;
$im->setscanline(y=>$y, pixels=>$row);
}
getscanline()
Read all or part of a horizontal line of pixels from an image. This method is most
useful in conjunction with "setscanline()".
The parameters you can pass are:
• "y" - vertical position of the scan line. This parameter is required.
• "x" - position to start on the scan line. Default: 0
• "width" - number of pixels to read. Default: $img->getwidth - x
• "type" - the type of pixel data to return. Default: "8bit".
Permitted values are "8bit" and "float" and "index".
In list context this method will return a list of Imager::Color objects when type is
"8bit", or a list of Imager::Color::Float objects when type if "float", or a list of
integers when type is "index".
In scalar context this returns a packed 8-bit pixels when type is "8bit", or a list of
packed floating point pixels when type is "float", or packed palette color indexes
when type is "index".
The values of samples for which the image does not have channels is undefined. For
example, for a single channel image the values of channels 1 through 3 are undefined.
Check image for a given color:
my $found;
YLOOP: for my $y (0..$img->getheight-1) {
my @colors = $img->getscanline(y=>$y);
for my $color (@colors) {
my ($red, $green, $blue, $alpha) = $color->rgba;
if ($red == $test_red && $green == $test_green && $blue == $test_blue
&& $alpha == $test_alpha) {
++$found;
last YLOOP;
}
}
}
Or do it using packed data:
my $found;
my $test_packed = pack("CCCC", $test_red, $test_green, $test_blue,
$test_alpha);
YLOOP: for my $y (0..$img->getheight-1) {
my $colors = $img->getscanline(y=>$y);
while (length $colors) {
if (substr($colors, 0, 4, '') eq $test_packed) {
++$found;
last YLOOP;
}
}
}
Some of the examples for "setscanline()" for more examples.
getsamples()
Read specified channels from all or part of a horizontal line of pixels from an image.
The parameters you can pass are:
• "y" - vertical position of the scan line. This parameter is required.
• "x" - position to start on the scan line. Default: 0
• "width" - number of pixels to read. Default: "$img->getwidth - x"
• "type" - the type of sample data to return. Default: "8bit".
Permitted values are "8bit" and "float".
As of Imager 0.61 this can be "16bit" only for 16 bit images.
• "channels" - a reference to an array of channels to return, where 0 is the first
channel. Default: "[ 0 .. $self->getchannels()-1 ]"
• "target" - if an array reference is supplied in target then the samples will be
stored here instead of being returned.
• "offset" - the offset within the array referenced by target
In list context this will return a list of integers between 0 and 255 inclusive when
type is "8bit", or a list of floating point numbers between 0.0 and 1.0 inclusive when
type is "float".
In scalar context this will return a string of packed bytes, as with " pack("C*", ...)
" when type is "8bit" or a string of packed doubles as with " pack("d*", ...) " when
type is "float".
If the target option is supplied then only a count of samples is returned.
Example: Check if any pixels in an image have a non-zero alpha channel:
my $has_coverage;
for my $y (0 .. $img->getheight()-1) {
my $alpha = $img->getsamples(y=>$y, channels=>[0]);
if ($alpha =~ /[^\0]/) {
++$has_coverage;
last;
}
}
Example: Convert a 2 channel gray image into a 4 channel RGBA image:
# this could be done with convert() instead
my $out = Imager->new(xsize => $src->getwidth(),
ysize => $src->getheight(),
channels => 4);
for my $y ( 0 .. $src->getheight()-1 ) {
my $data = $src->getsamples(y=>$y, channels=>[ 0, 0, 0, 1 ]);
$out->setscanline(y=>$y, pixels=>$data);
}
Retrieve 16-bit samples:
if ($img->bits == 16) {
my @samples;
$img->getsamples(x => 0, y => $y, target => \@samples, type => '16bit');
}
setsamples()
This allows writing of samples to an image.
Parameters:
• "y" - vertical position of the scan line. This parameter is required.
• "x" - position to start on the scan line. Default: 0
• "width" - number of pixels to write. Default: "$img->getwidth - x". The minimum
of this and the number of pixels represented by the samples provided will be
written.
• "type" - the type of sample data to write. This parameter is required.
This can be "8bit", "float" or for 16-bit images only, "16bit".
• "channels" - a reference to an array of channels to return, where 0 is the first
channel. Default: "[ 0 .. $self->getchannels()-1 ]"
• "data" - for a type of "8bit" or "float" this can be a reference to an array of
samples or a scalar containing packed samples. If "data" is a scalar it may only
contain characters from \x00 to \xFF.
For a type of "16bit" this can only be a reference to an array of samples to
write.
Required.
• "offset" - the starting offset within the array referenced by data. If "data" is
a scalar containing packed samples this offset is in samples.
Returns the number of samples written.
$targ->setsamples(y => $y, data => \@data);
$targ->setsamples(y => $y, data => \@data, offset => $src->getchannels);
Copy from one image to another:
my $targ = Imager->new(xsize => $src->getwidth,
ysize => $src->getheight, channels => $src->getchannels);
for my $y (0 .. $targ->getheight()-1) {
my $row = $src->getsamples(y => $y)
or die $src->errstr;
$targ->setsamples(y => $y, data => $row)
or die $targ->errstr;;
}
Compose an image from separate source channels:
my @src = ...; # images to work from, up to 4
my $targ = Imager->new(xsize => $src[0]->getwidth,
ysize => $src[0]->getheight, channels => scalar(@src));
for my $y (0 .. $targ->getheight()-1) {
for my $ch (0 .. $#src) {
my $row = $src[$ch]->getsamples(y => $y, channels => [ 0 ]);
$targ->setsamples(y => $y, data => $row, channels => [ $ch ] );
}
}
Packed Color Data
The getscanline() and setscanline() methods can work with pixels packed into scalars.
This is useful to remove the cost of creating color objects, but should only be used when
performance is an issue.
The getsamples() and setsamples() methods can work with samples packed into scalars.
Packed data can either be 1 byte per sample or 1 double per sample.
Each pixel returned by getscanline() or supplied to setscanline() contains 4 samples, even
if the image has fewer then 4 channels. The values of the extra samples as returned by
getscanline() is not specified. The extra samples passed to setscanline() are ignored.
To produce packed 1 byte/sample pixels, use the pack "C" template:
my $packed_8bit_pixel = pack("CCCC", $red, $blue, $green, $alpha);
To produce packed double/sample pixels, use the pack "d" template:
my $packed_float_pixel = pack("dddd", $red, $blue, $green, $alpha);
Note that double/sample data is always stored using the C "double" type, never "long
double", even if "perl" is built with "-Duselongdouble".
If you use a type parameter of "index" then the values are palette color indexes, not
sample values:
my $im = Imager->new(xsize => 100, ysize => 100, type => 'paletted');
my $black_index = $im->addcolors(colors => [ 'black' ]);
my $red_index = $im->addcolors(colors => [ 'red' ]);
# 2 pixels
my $packed_index_data = pack("C*", $black_index, $red_index);
$im->setscanline(y => $y, pixels => $packed_index_data, type => 'index');
Combine Types
Some methods accept a "combine" parameter, this can be any of the following:
"none"
The fill pixel replaces the target pixel.
"normal"
The fill pixels alpha value is used to combine it with the target pixel.
"multiply"
"mult"
Each channel of fill and target is multiplied, and the result is combined using the
alpha channel of the fill pixel.
"dissolve"
If the alpha of the fill pixel is greater than a random number, the fill pixel is
alpha combined with the target pixel.
"add"
The channels of the fill and target are added together, clamped to the range of the
samples and alpha combined with the target.
"subtract"
The channels of the fill are subtracted from the target, clamped to be >= 0, and alpha
combined with the target.
"diff"
The channels of the fill are subtracted from the target and the absolute value taken
this is alpha combined with the target.
"lighten"
The higher value is taken from each channel of the fill and target pixels, which is
then alpha combined with the target.
"darken"
The higher value is taken from each channel of the fill and target pixels, which is
then alpha combined with the target.
"hue"
The combination of the saturation and value of the target is combined with the hue of
the fill pixel, and is then alpha combined with the target.
"sat"
The combination of the hue and value of the target is combined with the saturation of
the fill pixel, and is then alpha combined with the target.
"value"
The combination of the hue and value of the target is combined with the value of the
fill pixel, and is then alpha combined with the target.
"color"
The combination of the value of the target is combined with the hue and saturation of
the fill pixel, and is then alpha combined with the target.
combines()
Returns a list of possible combine types.
BUGS
box() does not support anti-aliasing yet. Default color is not unified yet.
AUTHOR
Tony Cook <tonyc@cpan.org>, Arnar M. Hrafnkelsson.
SEE ALSO
Imager(3), Imager::Cookbook(3)
REVISION
$Revision$