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);
# Convert the image to GIF and print it on standard output
print $im->gif;
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 GIF 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:
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);
# Convert the image to GIF and print it on standard output
print $im->gif;
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 GIF, 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
5. When you're done drawing, you can convert the image
into GIF format by sending it a gif() 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.
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.
newFromGif
GD::Image::newFromGif(FILEHANDLE) class method
This will create an image from a GIF file read in
through the provided filehandle. The filehandle must
previously have been opened on a valid GIF 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 GIF file, the call returns undef. Notice that
the call doesn't automatically close the filehandle
for you.
To get information about the size and color usage of
the information, you can call the image query methods
described below.
Example usage:
open (GIF,"barnswallow.gif") || die;
$myImage = newFromGif GD::Image(GIF) || die;
close GIF;
newFromXbm
GD::Image::newFromXbm(FILEHANDLE) class method
reads the contents of an X Bitmap file:
open (XBM,"coredump.xbm") || die;
$myImage = newFromXbm GD::Image(XBM) || die;
close XBM;
newFromGd
GD::Image::newFromGd(FILEHANDLE) class method
This works in exactly the same way as newFromGif, 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 GIF 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;
gif GD::Image::gif object method
This returns the image data in GIF format. You can
then print it, pipe it to a display program, or write
it to a file. Example:
$gif_data = $myImage->gif;
open (DISPLAY,"| display -") || die;
print DISPLAY $gif_data;
close DISPLAY;
gd 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:
print MYOUTFILE $myImage->gd;
Color Control
colorAllocate
GD::Image::colorAllocate(red,green,blue) object
method
This allocates a color with the specified red, green
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
GD::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
GD::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
GD::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.
warn "Everything's coming up roses.\n" if $rosey >= 0;
colorsTotal
GD::Image::colorsTotal) object method
This returns the total number of colors allocated in
the object.
$maxColors = $myImage->colorsTotal;
getPixel
GD::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 GD::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
GD::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 GIF
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:
$im = newFromGif GD::Image(GIF);
$white = $im->colorClosest(255,255,255); # find white
$im->transparent($white);
print $im->gif;
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
GD::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
GD::Image::setStyle(@colors) and GD::gdStyled
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
GD::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:
$myImage->setPixel(50,50,$peach);
line GD::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
GD::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
GD::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
# read in a fill pattern and set it
open(GIF,"happyface.gif") || die;
$tile = newFromGif GD::Image(GIF);
$myImage->setTile($tile);
# draw the rectangle, filling it with the pattern
$myImage->filledRectangle(10,10,150,200,gdTiled);
polygon
GD::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
GD::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 GD::Image::arc(cx,cy,width,height,start,end,color)
object method
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 GD::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);
GD::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);
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 GD::Image::copy(sourceImage,dstX,dstY,srcX,srcY,width,height)
object method
This is the simpler of the two 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);
copyResized
GD::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 accomodate the size
requirements.
Example:
... 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 gdLargeFont, gdMediumBoldFont,
gdSmallFont and gdTinyFont. Currently there is no way of
dynamically creating your own fonts.
string
GD::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
and gdLargeFont.
Example:
$myImage->string(gdSmallFont,2,10,"Peachy Keen",$peach);
stringUp
GD::Image::stringUp(font,x,y,string,color) Object
Method
Just like the previous call, but draws the text
rotated counterclockwise 90 degrees.
char
charUp
GD::Image::char(font,x,y,char,color) Object Method
GD::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.
interlaced
GD::Image::interlaced( ) GD::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.
c<getBounds>
GD::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.
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).
c<new>
GD::Polygon::new class method
Create an empty polygon with no vertices.
$poly = new GD::Polygon;
addPt
GD::Polygon::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,$blue);
getPt
GD::Polygon::getPt(index) object method
Retrieve the point at the specified vertex.
($x,$y) = $poly->getPt(2);
GD::Polygon::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.
$poly->setPt(2,100,100);
deletePt
GD::Polygon:deletePt(index) object method
Delete the specified vertex, returning its value.
($x,$y) = $poly->deletePt(1);
toPt GD::Polygon::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
GD::Polygon::length object method
Return the number of vertices in the polygon.
$points = $poly->length;
vertices
GD::Polygon::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
GD::Polygon::bounds object method
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
GD::Polygon::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 GD::Polygon::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
GD::Polygon::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
GD::Polygon::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
Font Utilities
Gd's support for fonts is minimal. Basically you have
access to gdSmallFont and gdLargeFont for drawing, and not
much else. However, for future compatibility, I've made
the fonts into perl objects of type GD::Font that you can
query and, perhaps someday manipulate.
gdSmallFont
GD::Font::gdSmallFont constant
This is the basic small font, "borrowed" from a well
known public domain 6x12 font.
gdLargeFont
GD::Font::gdLargeFont constant
This is the basic large font, "borrowed" from a well
known public domain 8x16 font.
gdMediumBoldFont
GD::Font::gdMediumBoldFont 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::gdTinyFont constant
This is a tiny, almost unreadable font, 5x8 pixels
wide.
nchars
GD::Font::nchars object method
This returns the number of characters in the font.
print "The large font contains ",gdLargeFont->nchars," characters\n";
offset
GD::Font::offset object method
This returns the ASCII value of the first character
in the font
width
height
GD::Font::width GD::Font::height object methods
($w,$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/gd.html. 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, Lincoln D. Stein.
You are free to use it for any purpose, commercial or
noncommercial, provided that if you redistribute the
source code this statement of copyright remains attached.
The gd library is covered separately under a 1994
copyright by Quest Protein Database Center, Cold Spring
Harbor Labs and Thomas Boutell. For usage information see
the gd documentation at URL
http://www.boutell.com/gd/gd.html
The latest versions of GD.pm are available at
http://www.genome.wi.mit.edu/ftp/pub/software/WWW/GD.html
ftp://ftp-genome.wi.mit.edu/pub/software/WWW/GD.pm.tar.gz