Provided by: wml_2.0.12ds1-7_amd64 
NAME
GD.pm - Interface to Gd Graphics Library
SYNOPSIS
use GD;
# create a new image
$im = new GD::Image(100,100);
# allocate some colors
$white = $im->colorAllocate(255,255,255);
$black = $im->colorAllocate(0,0,0);
$red = $im->colorAllocate(255,0,0);
$blue = $im->colorAllocate(0,0,255);
# make the background transparent and interlaced
$im->transparent($white);
$im->interlaced('true');
# Put a black frame around the picture
$im->rectangle(0,0,99,99,$black);
# Draw a blue oval
$im->arc(50,50,95,75,0,360,$blue);
# And fill it with red
$im->fill(50,50,$red);
# make sure we are writing to a binary stream
binmode STDOUT;
# Convert the image to PNG and print it on standard output
print $im->png;
DESCRIPTION
GD.pm is a port of Thomas Boutell's gd graphics library (see below). GD allows you to create color
drawings using a large number of graphics primitives, and emit the drawings as PNG files.
GD defines the following three classes:
"GD::Image"
An image class, which holds the image data and accepts graphic primitive method calls.
"GD::Font"
A font class, which holds static font information and used for text rendering.
"GD::Polygon"
A simple polygon object, used for storing lists of vertices prior to rendering a polygon into an
image.
A Simple Example:
#!/usr/local/bin/perl
use GD;
# create a new image
$im = new GD::Image(100,100);
# allocate some colors
$white = $im->colorAllocate(255,255,255);
$black = $im->colorAllocate(0,0,0);
$red = $im->colorAllocate(255,0,0);
$blue = $im->colorAllocate(0,0,255);
# make the background transparent and interlaced
$im->transparent($white);
$im->interlaced('true');
# Put a black frame around the picture
$im->rectangle(0,0,99,99,$black);
# Draw a blue oval
$im->arc(50,50,95,75,0,360,$blue);
# And fill it with red
$im->fill(50,50,$red);
# make sure we are writing to a binary stream
binmode STDOUT;
# Convert the image to PNG and print it on standard output
print $im->png;
Notes:
1. To create a new, empty image, send a new() message to GD::Image, passing it the width and height of
the image you want to create. An image object will be returned. Other class methods allow you to
initialize an image from a preexisting PNG, GD or XBM file.
2. Next you will ordinarily add colors to the image's color table. colors are added using a
colorAllocate() method call. The three parameters in each call are the red, green and blue (rgb) triples
for the desired color. The method returns the index of that color in the image's color table. You
should store these indexes for later use.
3. Now you can do some drawing! The various graphics primitives are described below. In this example,
we do some text drawing, create an oval, and create and draw a polygon.
4. Polygons are created with a new() message to GD::Polygon. You can add points to the returned polygon
one at a time using the addPt() method. The polygon can then be passed to an image for rendering.
5. When you're done drawing, you can convert the image into PNG format by sending it a png() message. It
will return a (potentially large) scalar value containing the binary data for the image. Ordinarily you
will print it out at this point or write it to a file. To ensure portability to platforms that
differentiate between text and binary files, be sure to call "binmode()" on the file you are writing the
image to.
Method Calls
Creating and Saving Images
"new"
"GD::Image->new(width,height)" class method
To create a new, blank image, send a new() message to the GD::Image class. For example:
$myImage = new GD::Image(100,100) || die;
This will create an image that is 100 x 100 pixels wide. If you don't specify the dimensions, a
default of 64 x 64 will be chosen. If something goes wrong (e.g. insufficient memory), this call
will return undef.
"newFromPng"
"GD::Image->newFromPng(FILEHANDLE)" class method
This will create an image from a PNG file read in through the provided filehandle. The filehandle
must previously have been opened on a valid PNG file or pipe. If successful, this call will return
an initialized image which you can then manipulate as you please. If it fails, which usually
happens if the thing at the other end of the filehandle is not a valid PNG file, the call returns
undef. Notice that the call doesn't automatically close the filehandle for you. But it does call
"binmode(FILEHANDLE)" for you, on platforms where this matters.
To get information about the size and color usage of the information, you can call the image query
methods described below.
Example usage:
open (PNG,"barnswallow.png") || die;
$myImage = newFromPng GD::Image(PNG) || die;
close PNG;
"newFromXbm"
"GD::Image->newFromXbm(FILEHANDLE)" class method
This works in exactly the same way as "newFromPng", but reads the contents of an X Bitmap (black &
white) file:
open (XBM,"coredump.xbm") || die;
$myImage = newFromXbm GD::Image(XBM) || die;
close XBM;
Note that this function also calls "binmode(FILEHANDLE)" before reading from the filehandle.
"newFromXpm"
"GD::Image->newFromXpm($filename)" class method
This creates a new GD::Image object starting from a filename. This is unlike the other newFrom()
functions because it does not take a filehandle. This difference comes from an inconsistency in the
underlying gd library.
$myImage = newFromXpm GD::Image('earth.xpm') || die;
This function is only available if libgd was compiled with XPM support.
NOTE: As of version 1.7.3 of the libgd library, I can't get the underlying createFromXpm() function
to return a valid image -- I just get black.
"newFromGd2"
"GD::Image->newFromGd2(FILEHANDLE)" class method
This works in exactly the same way as "newFromgd()", but uses the new compressed GD2 image format.
"newFromGd"
"GD::Image->newFromGd(FILEHANDLE)" class method
This works in exactly the same way as "newFromPng", but reads the contents of a GD file. GD is Tom
Boutell's disk-based storage format, intended for the rare case when you need to read and write the
image to disk quickly. It's not intended for regular use, because, unlike PNG or JPEG, no image
compression is performed and these files can become BIG.
open (GDF,"godzilla.gd") || die;
$myImage = newFromGd GD::Image(GDF) || die;
close GDF;
Note that this function also calls "binmode(FILEHANDLE)" before reading from the supplied
filehandle.
"newFromGd2"
"GD::Image->newFromGd2(FILEHANDLE)" class method
This works in exactly the same way as "newFromgd()", but uses the new compressed GD2 image format.
"newFromGd2Part"
"GD::Image->newFromGd2Part(FILEHANDLE,srcX,srcY,width,height)" class method
This class method allows you to read in just a portion of a GD version 2 image file. In additionto
a filehandle, it accepts the top-left corner and dimensions (width,height) of the region of the
image to read. For example:
open (GDF,"godzilla.gd2") || die;
$myImage = GD::Image->newFromGd2Part(GDF,10,20,100,100) || die;
close GDF;
This reads a 100x100 square portion of the image starting from position (10,20).
"png"
"$image->png" object method
This returns the image data in PNG format. You can then print it, pipe it to a display program, or
write it to a file. Example:
$png_data = $myImage->png;
open (DISPLAY,"| display -") || die;
binmode DISPLAY;
print DISPLAY $png_data;
close DISPLAY;
Note the use of "binmode()". This is crucial for portability to DOSish platforms.
"gd" "$image->gd" object method
This returns the image data in GD format. You can then print it, pipe it to a display program, or
write it to a file. Example:
binmode MYOUTFILE;
print MYOUTFILE $myImage->gd;
"gd2"
"$image->gd2" object method
Same as gd(), except that it returns the data in compressed GD2 format.
Color Control
"colorAllocate"
"$image->colorAllocate(red,green,blue)" object method
This allocates a color with the specified red, green and blue components and returns its index in
the color table, if specified. The first color allocated in this way becomes the image's background
color. (255,255,255) is white (all pixels on). (0,0,0) is black (all pixels off). (255,0,0) is
fully saturated red. (127,127,127) is 50% gray. You can find plenty of examples in
/usr/X11/lib/X11/rgb.txt.
If no colors are allocated, then this function returns -1.
Example:
$white = $myImage->colorAllocate(0,0,0); #background color
$black = $myImage->colorAllocate(255,255,255);
$peachpuff = $myImage->colorAllocate(255,218,185);
"colorDeallocate"
"$image->colorDeallocate(colorIndex)" object method
This marks the color at the specified index as being ripe for reallocation. The next time
colorAllocate is used, this entry will be replaced. You can call this method several times to
deallocate multiple colors. There's no function result from this call.
Example:
$myImage->colorDeallocate($peachpuff);
$peachy = $myImage->colorAllocate(255,210,185);
"colorClosest"
"$image->colorClosest(red,green,blue)" object method
This returns the index of the color closest in the color table to the red green and blue components
specified. If no colors have yet been allocated, then this call returns -1.
Example:
$apricot = $myImage->colorClosest(255,200,180);
"colorExact"
"$image->colorExact(red,green,blue)" object method
This returns the index of a color that exactly matches the specified red green and blue components.
If such a color is not in the color table, this call returns -1.
$rosey = $myImage->colorExact(255,100,80);
warn "Everything's coming up roses.\n" if $rosey >= 0;
"colorResolve"
"$image->colorResolve(red,green,blue)" object method
This returns the index of a color that exactly matches the specified red green and blue components.
If such a color is not in the color table and there is room, then this method allocates the color in
the color table and returns its index.
$rosey = $myImage->colorResolve(255,100,80);
warn "Everything's coming up roses.\n" if $rosey >= 0;
"colorsTotal"
"$image->colorsTotal)" object method
This returns the total number of colors allocated in the object.
$maxColors = $myImage->colorsTotal;
"getPixel"
"$image->getPixel(x,y)" object method
This returns the color table index underneath the specified point. It can be combined with rgb() to
obtain the rgb color underneath the pixel.
Example:
$index = $myImage->getPixel(20,100);
($r,$g,$b) = $myImage->rgb($index);
"rgb"
"$image->rgb(colorIndex)" object method
This returns a list containing the red, green and blue components of the specified color index.
Example:
@RGB = $myImage->rgb($peachy);
"transparent"
"$image->transparent(colorIndex)" object method
This marks the color at the specified index as being transparent. Portions of the image drawn in
this color will be invisible. This is useful for creating paintbrushes of odd shapes, as well as
for making PNG backgrounds transparent for displaying on the Web. Only one color can be transparent
at any time. To disable transparency, specify -1 for the index.
If you call this method without any parameters, it will return the current index of the transparent
color, or -1 if none.
Example:
open(PNG,"test.png");
$im = newFromPng GD::Image(PNG);
$white = $im->colorClosest(255,255,255); # find white
$im->transparent($white);
binmode STDOUT;
print $im->png;
Special Colors
GD implements a number of special colors that can be used to achieve special effects. They are constants
defined in the GD:: namespace, but automatically exported into your namespace when the GD module is
loaded.
"setBrush"
"gdBrushed"
"$image->setBrush( )" and "GD::gdBrushed"
You can draw lines and shapes using a brush pattern. Brushes are just images that you can create
and manipulate in the usual way. When you draw with them, their contents are used for the color and
shape of the lines.
To make a brushed line, you must create or load the brush first, then assign it to the image using
"setBrush". You can then draw in that with that brush using the "gdBrushed" special color. It's
often useful to set the background of the brush to transparent so that the non-colored parts don't
overwrite other parts of your image.
Example:
# Create a brush at an angle
$diagonal_brush = new GD::Image(5,5);
$white = $diagonal_brush->allocateColor(255,255,255);
$black = $diagonal_brush->allocateColor(0,0,0);
$diagonal_brush->transparent($white);
$diagonal_brush->line(0,4,4,0,$black); # NE diagonal
# Set the brush
$myImage->setBrush($diagonal_brush);
# Draw a circle using the brush
$myImage->arc(50,50,25,25,0,360,gdBrushed);
"setStyle"
"gdStyled"
"$image->setStyle(@colors)" and "GD::gdStyled"
Styled lines consist of an arbitrary series of repeated colors and are useful for generating dotted
and dashed lines. To create a styled line, use "setStyle" to specify a repeating series of colors.
It accepts an array consisting of one or more color indexes. Then draw using the "gdStyled" special
color. Another special color, "gdTransparent" can be used to introduce holes in the line, as the
example shows.
Example:
# Set a style consisting of 4 pixels of yellow,
# 4 pixels of blue, and a 2 pixel gap
$myImage->setStyle($yellow,$yellow,$yellow,$yellow,
$blue,$blue,$blue,$blue,
gdTransparent,gdTransparent);
$myImage->arc(50,50,25,25,0,360,gdStyled);
To combine the "gdStyled" and "gdBrushed" behaviors, you can specify "gdStyledBrushed". In this
case, a pixel from the current brush pattern is rendered wherever the color specified in setStyle()
is neither gdTransparent nor 0.
"gdTiled"
Draw filled shapes and flood fills using a pattern. The pattern is just another image. The image
will be tiled multiple times in order to fill the required space, creating wallpaper effects. You
must call "setTile" in order to define the particular tile pattern you'll use for drawing when you
specify the gdTiled color. details.
"gdStyled"
The gdStyled color is used for creating dashed and dotted lines. A styled line can contain any
series of colors and is created using the "setStyled" command.
Drawing Commands
"setPixel"
"$image->setPixel(x,y,color)" object method
This sets the pixel at (x,y) to the specified color index. No value is returned from this method.
The coordinate system starts at the upper left at (0,0) and gets larger as you go down and to the
right. You can use a real color, or one of the special colors gdBrushed, gdStyled and
gdStyledBrushed can be specified.
Example:
# This assumes $peach already allocated
$myImage->setPixel(50,50,$peach);
"line"
"$image->line(x1,y1,x2,y2,color)" object method
This draws a line from (x1,y1) to (x2,y2) of the specified color. You can use a real color, or one
of the special colors gdBrushed, gdStyled and gdStyledBrushed.
Example:
# Draw a diagonal line using the currently defind
# paintbrush pattern.
$myImage->line(0,0,150,150,gdBrushed);
"dashedLine"
"$image->dashedLine(x1,y1,x2,y2,color)" object method
This draws a dashed line from (x1,y1) to (x2,y2) in the specified color. A more powerful way to
generate arbitrary dashed and dotted lines is to use the setStyle() method described below and to
draw with the special color gdStyled.
Example:
$myImage->dashedLine(0,0,150,150,$blue);
"rectangle"
"GD::Image::rectangle(x1,y1,x2,y2,color)" object method
This draws a rectangle with the specified color. (x1,y1) and (x2,y2) are the upper left and lower
right corners respectively. Both real color indexes and the special colors gdBrushed, gdStyled and
gdStyledBrushed are accepted.
Example:
$myImage->rectangle(10,10,100,100,$rose);
"filledRectangle"
"$image->filledRectangle(x1,y1,x2,y2,color)" object method
This draws a rectangle filed with the specified color. You can use a real color, or the special
fill color gdTiled to fill the polygon with a pattern.
Example:
# read in a fill pattern and set it
open(PNG,"happyface.png") || die;
$tile = newFromPng GD::Image(PNG);
$myImage->setTile($tile);
# draw the rectangle, filling it with the pattern
$myImage->filledRectangle(10,10,150,200,gdTiled);
"polygon"
"$image->polygon(polygon,color)" object method
This draws a polygon with the specified color. The polygon must be created first (see below). The
polygon must have at least three vertices. If the last vertex doesn't close the polygon, the method
will close it for you. Both real color indexes and the special colors gdBrushed, gdStyled and
gdStyledBrushed can be specified.
Example:
$poly = new GD::Polygon;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
$myImage->polygon($poly,$blue);
"filledPolygon"
"$image->filledPolygon(poly,color)" object method
This draws a polygon filled with the specified color. You can use a real color, or the special fill
color gdTiled to fill the polygon with a pattern.
Example:
# make a polygon
$poly = new GD::Polygon;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
# draw the polygon, filling it with a color
$myImage->filledPolygon($poly,$peachpuff);
"arc"
"$image->arc(cx,cy,width,height,start,end,color)" object method
This draws arcs and ellipses. (cx,cy) are the center of the arc, and (width,height) specify the
width and height, respectively. The portion of the ellipse covered by the arc are controlled by
start and end, both of which are given in degrees from 0 to 360. Zero is at the top of the ellipse,
and angles increase clockwise. To specify a complete ellipse, use 0 and 360 as the starting and
ending angles. To draw a circle, use the same value for width and height.
You can specify a normal color or one of the special colors gdBrushed, gdStyled, or gdStyledBrushed.
Example:
# draw a semicircle centered at 100,100
$myImage->arc(100,100,50,50,0,180,$blue);
"fill"
"$image->fill(x,y,color)" object method
This method flood-fills regions with the specified color. The color will spread through the image,
starting at point (x,y), until it is stopped by a pixel of a different color from the starting pixel
(this is similar to the "paintbucket" in many popular drawing toys). You can specify a normal
color, or the special color gdTiled, to flood-fill with patterns.
Example:
# Draw a rectangle, and then make its interior blue
$myImage->rectangle(10,10,100,100,$black);
$myImage->fill(50,50,$blue);
"$image->fillToBorder(x,y,bordercolor,color)" object method
Like "fill", this method flood-fills regions with the specified color, starting at position (x,y).
However, instead of stopping when it hits a pixel of a different color than the starting pixel,
flooding will only stop when it hits the color specified by bordercolor. You must specify a normal
indexed color for the bordercolor. However, you are free to use the gdTiled color for the fill.
Example:
# This has the same effect as the previous example
$myImage->rectangle(10,10,100,100,$black);
$myImage->fillToBorder(50,50,$black,$blue);
Image Copying Commands
Two methods are provided for copying a rectangular region from one image to another. One method copies a
region without resizing it. The other allows you to stretch the region during the copy operation.
With either of these methods it is important to know that the routines will attempt to flesh out the
destination image's color table to match the colors that are being copied from the source. If the
destination's color table is already full, then the routines will attempt to find the best match, with
varying results.
"copy"
"$image->copy(sourceImage,dstX,dstY,srcX,srcY,width,height)" object method
This is the simplest of the several copy operations, copying the specified region from the source
image to the destination image (the one performing the method call). (srcX,srcY) specify the upper
left corner of a rectangle in the source image, and (width,height) give the width and height of the
region to copy. (dstX,dstY) control where in the destination image to stamp the copy. You can use
the same image for both the source and the destination, but the source and destination regions must
not overlap or strange things will happen.
Example:
$myImage = new GD::Image(100,100);
... various drawing stuff ...
$srcImage = new GD::Image(50,50);
... more drawing stuff ...
# copy a 25x25 pixel region from $srcImage to
# the rectangle starting at (10,10) in $myImage
$myImage->copy($srcImage,10,10,0,0,25,25);
"clone"
"$image->clone()" object method
Make a copy of the image and return it as a new object. The new image will look identical.
However, it may differ in the size of the color palette and other nonessential details.
Example:
$myImage = new GD::Image(100,100);
... various drawing stuff ...
$copy = $myImage->clone;
"$image->copyMerge(sourceImage,dstX,dstY,srcX,srcY,width,height,percent)" object method
This copies the indicated rectangle from the source image to the destination image, merging the
colors to the extent specified by percent (an integer between 0 and 100). Specifying 100% has the
same effect as copy() -- replacing the destination pixels with the source image. This is most
useful for highlighting an area by merging in a solid rectangle.
Example:
$myImage = new GD::Image(100,100);
... various drawing stuff ...
$redImage = new GD::Image(50,50);
... more drawing stuff ...
# copy a 25x25 pixel region from $srcImage to
# the rectangle starting at (10,10) in $myImage, merging 50%
$myImage->copyMerge($srcImage,10,10,0,0,25,25,50);
"$image->copyMergeGray(sourceImage,dstX,dstY,srcX,srcY,width,height,percent)" object method
This is identical to copyMerge() except that it preserves the hue of the source by converting all
the pixels of the destination rectangle to grayscale before merging.
"copyResized"
"$image->copyResized(sourceImage,dstX,dstY,srcX,srcY,destW,destH,srcW,srcH)" object method
This method is similar to copy() but allows you to choose different sizes for the source and
destination rectangles. The source and destination rectangle's are specified independently by
(srcW,srcH) and (destW,destH) respectively. copyResized() will stretch or shrink the image to
accommodate the size requirements.
Example:
$myImage = new GD::Image(100,100);
... various drawing stuff ...
$srcImage = new GD::Image(50,50);
... more drawing stuff ...
# copy a 25x25 pixel region from $srcImage to
# a larger rectangle starting at (10,10) in $myImage
$myImage->copyResized($srcImage,10,10,0,0,50,50,25,25);
Character and String Drawing
Gd allows you to draw characters and strings, either in normal horizontal orientation or rotated 90
degrees. These routines use a GD::Font object, described in more detail below. There are four built-in
fonts, available in global variables gdGiantFont, gdLargeFont, gdMediumBoldFont, gdSmallFont and
gdTinyFont. Currently there is no way of dynamically creating your own fonts.
"string"
"$image->string(font,x,y,string,color)" Object Method
This method draws a string startin at position (x,y) in the specified font and color. Your choices
of fonts are gdSmallFont, gdMediumBoldFont, gdTinyFont, gdLargeFont and gdGiantFont.
Example:
$myImage->string(gdSmallFont,2,10,"Peachy Keen",$peach);
"stringUp"
"$image->stringUp(font,x,y,string,color)" Object Method
Just like the previous call, but draws the text rotated counterclockwise 90 degrees.
"char"
"charUp"
"$image->char(font,x,y,char,color)" Object Method "$image->charUp(font,x,y,char,color)" Object
Method
These methods draw single characters at position (x,y) in the specified font and color. They're
carry-overs from the C interface, where there is a distinction between characters and strings. Perl
is insensible to such subtle distinctions.
"stringTTF"
"@bounds = $image->stringTTF(fgcolor,fontname,ptsize,angle,x,y,string)" Object Method "@bounds =
GD::Image->stringTTF(fgcolor,fontname,ptsize,angle,x,y,string)" Class Method
This method uses TrueType to draw a scaled, antialiased string using the TrueType vector font of
your choice. It requires that libgd to have been compiled with TrueType support, and for the
appropriate TrueType font to be installed on your system.
The arguments are as follows:
fgcolor Color index to draw the string in
fontname An absolute or relative path to the TrueType (.ttf) font file
ptsize The desired point size (may be fractional)
angle The rotation angle, in radians
x,y X and Y coordinates to start drawing the string
string The string itself
If successful, the method returns an eight-element list giving the boundaries of the rendered
string:
@bounds[0,1] Lower left corner (x,y)
@bounds[2,3] Lower right corner (x,y)
@bounds[4,5] Upper right corner (x,y)
@bounds[6,7] Upper left corner (x,y)
In case of an error (such as the font not being available, or TTF support not being available), the
method returns an empty list and sets $@ to the error message.
You may also call this method from the GD::Image class name, in which case it doesn't do any actual
drawing, but returns the bounding box using an inexpensive operation. You can use this to perform
layout operations prior to drawing.
Miscellaneous Image Methods
"interlaced"
"$image->interlaced( )" "$image->interlaced(1)" Object method
This method sets or queries the image's interlaced setting. Interlace produces a cool venetian
blinds effect on certain viewers. Provide a true parameter to set the interlace attribute. Provide
undef to disable it. Call the method without parameters to find out the current setting.
"getBounds"
"$image->getBounds( )" Object method
This method will return a two-member list containing the width and height of the image. You query
but not not change the size of the image once it's created.
"compare"
"$image1->compare($image2)"
Compare two images and return a bitmap describing the differenes found, if any. The return value
must be logically ANDed with one or more constants in order to determine the differences. The
following constants are available:
GD_CMP_IMAGE The two images look different
GD_CMP_NUM_COLORS The two images have different numbers of colors
GD_CMP_COLOR The two images' palettes differ
GD_CMP_SIZE_X The two images differ in the horizontal dimension
GD_CMP_SIZE_Y The two images differ in the vertical dimension
GD_CMP_TRANSPARENT The two images have different transparency
GD_CMP_BACKGROUND The two images have different background colors
GD_CMP_INTERLACE The two images differ in their interlace
The most important of these is GD_CMP_IMAGE, which will tell you whether the two images will look
different, ignoring differences in the order of colors in the color palette and other invisible
changes. The constants are not imported by default, but must be imported individually or by
importing the :cmp tag. Example:
use GD qw(:DEFAULT :cmp);
# get $image1 from somewhere
# get $image2 from somewhere
if ($image1->compare($image2) & GD_CMP_IMAGE) {
warn "images differ!";
}
Polygon Methods
A few primitive polygon creation and manipulation methods are provided. They aren't part of the Gd
library, but I thought they might be handy to have around (they're borrowed from my qd.pl Quickdraw
library).
"new"
"GD::Polygon->new" class method
Create an empty polygon with no vertices.
$poly = new GD::Polygon;
"addPt"
"$poly->addPt(x,y)" object method
Add point (x,y) to the polygon.
$poly->addPt(0,0);
$poly->addPt(0,50);
$poly->addPt(25,25);
$myImage->fillPoly($poly,$blue);
"getPt"
"$poly->getPt(index)" object method
Retrieve the point at the specified vertex.
($x,$y) = $poly->getPt(2);
"setPt"
"$poly->setPt(index,x,y)" object method
Change the value of an already existing vertex. It is an error to set a vertex that isn't already
defined.
$poly->setPt(2,100,100);
"deletePt"
"$poly->deletePt(index)" object method
Delete the specified vertex, returning its value.
($x,$y) = $poly->deletePt(1);
"toPt"
"$poly->toPt(dx,dy)" object method
Draw from current vertex to a new vertex, using relative (dx,dy) coordinates. If this is the first
point, act like addPt().
$poly->addPt(0,0);
$poly->toPt(0,50);
$poly->toPt(25,-25);
$myImage->fillPoly($poly,$blue);
"length"
"$poly->length" object method
Return the number of vertices in the polygon.
$points = $poly->length;
"vertices"
"$poly->vertices" object method
Return a list of all the verticies in the polygon object. Each membver of the list is a reference
to an (x,y) array.
@vertices = $poly->vertices;
foreach $v (@vertices)
print join(",",@$v),"\n";
}
"bounds"
"$poly->bounds" object method
Return the smallest rectangle that completely encloses the polygon. The return value is an array
containing the (left,top,right,bottom) of the rectangle.
($left,$top,$right,$bottom) = $poly->bounds;
"offset"
"$poly->offset(dx,dy)" object method
Offset all the vertices of the polygon by the specified horizontal (dh) and vertical (dy) amounts.
Positive numbers move the polygon down and to the right.
$poly->offset(10,30);
"map"
"$poly->map(srcL,srcT,srcR,srcB,destL,dstT,dstR,dstB)" object method
Map the polygon from a source rectangle to an equivalent position in a destination rectangle, moving
it and resizing it as necessary. See polys.pl for an example of how this works. Both the source
and destination rectangles are given in (left,top,right,bottom) coordinates. For convenience, you
can use the polygon's own bounding box as the source rectangle.
# Make the polygon really tall
$poly->map($poly->bounds,0,0,50,200);
"scale"
"$poly->scale(sx,sy)" object method
Scale each vertex of the polygon by the X and Y factors indicated by sx and sy. For example
scale(2,2) will make the polygon twice as large. For best results, move the center of the polygon
to position (0,0) before you scale, then move it back to its previous position.
"transform"
"$poly->transform(sx,rx,sy,ry,tx,ty)" object method
Run each vertex of the polygon through a transformation matrix, where sx and sy are the X and Y
scaling factors, rx and ry are the X and Y rotation factors, and tx and ty are X and Y offsets. See
the Adobe PostScript Reference, page 154 for a full explanation, or experiment.
Font Utilities
The libgd library (used by the Perl GD library) has built-in support for about half a dozen fonts, which
were converted from public-domain X Windows fonts. For more fonts, compile libgd with TrueType support
and use the stringTTF() call.
If you wish to add more built-in fonts, the directory bdf_scripts contains two contributed utilities that
may help you convert X-Windows BDF-format fonts into the format that libgd uses internally. However
these scripts were written for earlier versions of GD which included its own mini-gd library. These
scripts will have to be adapted for use with libgd, and the libgd library itself will have to be
recompiled and linked! Please do not contact me for help with these scripts: they are unsupported.
"gdSmallFont"
"GD::Font->Small" constant
This is the basic small font, "borrowed" from a well known public domain 6x12 font.
"gdLargeFont"
"GD::Font->Large" constant
This is the basic large font, "borrowed" from a well known public domain 8x16 font.
"gdMediumBoldFont"
"GD::Font->MediumBold" constant
This is a bold font intermediate in size between the small and large fonts, borrowed from a public
domain 7x13 font;
"gdTinyFont"
"GD::Font->Tiny" constant
This is a tiny, almost unreadable font, 5x8 pixels wide.
"gdGiantFont"
"GD::Font->Giant" constant
This is a 9x15 bold font converted by Jan Pazdziora from a sans serif X11 font.
"nchars"
"$font->nchars" object method
This returns the number of characters in the font.
print "The large font contains ",gdLargeFont->nchars," characters\n";
"offset"
"$font->offset" object method
This returns the ASCII value of the first character in the font
"width"
"height"
"$font->width" "GD::Font::height" object methods
These return the width and height of the font.
($w,$h) = (gdLargeFont->width,gdLargeFont->height);
Obtaining the C-language version of gd
libgd, the C-language version of gd, can be obtained at URL http://www.boutell.com/gd/. Directions for installing and using it can be found at that site. Please do not contact me for help with libgd.
Copyright Information
The GD.pm interface is copyright 1995-1999, Lincoln D. Stein. It is distributed under the same terms as
Perl itself. See the "Artistic License" in the Perl source code distribution for licensing terms.
The latest versions of GD.pm are available at
http://stein.cshl.org/WWW/software/GD