GD.pm - Interface to Gd Graphics Library
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;
GD.pm is a Perl interface to Thomas Boutell's gd graphics library (version 2.01 or higher; 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::ImageGD::FontGD::PolygonA 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:
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 JPG, PNG, GD, GD2 or XBM file.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.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.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.
The following class methods allow you to create new GD::Image objects.
new() method is the main constructor for the GD::Image class.
Called with two integer arguments, it creates a new blank image of the
specified width and height. 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.
The optional third argument, $truecolor, tells new() to create a
truecolor GD::Image object. Truecolor images have 24 bits of color
data (eight bits each in the red, green and blue channels
respectively), allowing for precise photograph-quality color usage.
If not specified, the image will use an 8-bit palette for
compatibility with older versions of libgd.
Alternatively, you may create a GD::Image object based on an existing image by providing an open filehandle, a filename, or the image data itself. The image formats automatically recognized and accepted are: PNG, JPEG, XPM and GD2. Other formats, including WBMP, and GD version 1, cannot be recognized automatically at this time.
If something goes wrong (e.g. insufficient memory), this call will return undef.
GD::Image->trueColor(1);
somewhere before creating new images. To switch back to palette based by default, use:
GD::Image->trueColor(0);
newPalette() and newTrueColor() methods can be used to explicitly
create an palette based or true color image regardless of the
current setting of trueColor().
newFromPng() method will create an image from a PNG file read in
through the provided filehandle or file path. 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.
The optional $truecolor (0/1) value can be used to override the global
setting of trueColor() to specify if the return image should be
palette-based or truecolor.
You may use any of the following as the argument:
1) a simple filehandle, such as STDIN 2) a filehandle glob, such as *PNG 3) a reference to a glob, such as \*PNG 4) an IO::Handle object 5) the pathname of a file
In the latter case, newFromPng() will attempt to open the file for you
and read the PNG information from it.
Example1:
open (PNG,"barnswallow.png") || die; $myImage = newFromPng GD::Image(\*PNG) || die; close PNG;
Example2:
$myImage = newFromPng GD::Image('barnswallow.png');
To get information about the size and color usage of the information, you can call the image query methods described below.
The newFromPngData() method will create a new GD::Image initialized
with the PNG format data contained in $data.
newFromPng() and newFromPngData(), and will accept the same
filehandle and pathname arguments.
The optional $truecolor (0/1) value can be used to override the global
setting of trueColor() to specify if the return image should be
palette-based or truecolor.
Bear in mind that JPEG is a 24-bit format, while GD is 8-bit. This means that photographic images will become posterized.
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;
There is no newFromXbmData() function, because there is no
corresponding function in the gd library.
newFromWMPData() method.
$myImage = newFromGd GD::Image("godzilla.gd") || die;
close GDF;
newFromGd() and
newFromGdData, but use the new compressed GD2 image format.
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).
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: The libgd library is unable to read certain XPM files, returning an all-black image instead.
Once a GD::Image object is created, you can draw with it, copy it, and merge two images. When you are finished manipulating the object, you can convert it into a standard image file format to output or save to a file.
The following methods convert the internal drawing format into standard output file formats.
$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.
The optional $compression_level argument controls the amount of
compression to apply to the output PNG image. Values range from 0-9,
where 0 means no compression (largest files, highest quality) and 9
means maximum compression (smallest files, worst quality). A
compression level of -1 uses the default compression level selected
when zlib was compiled on your system, and is the same as calling
png() with no argument. Be careful not to confuse this argument with
the jpeg() quality argument, which ranges from 0-100 and has the
opposite meaning from compression (higher numbers give higher
quality).
jpeg() in order to control the JPEG quality.
This should be an integer between 0 and 100. Higher quality scores
give larger files and better image quality. If you don't specify the
quality, jpeg() will choose a good default.
binmode MYOUTFILE;
print MYOUTFILE $myImage->gd;
These methods allow you to control and manipulate the GD::Image color table.
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);
alphaBlending function changes the way this
alpha channel affects the resulting image.
alphaBlending function changes the way this
alpha channel affects the resulting image.
Example:
$myImage->colorDeallocate($peachpuff);
$peachy = $myImage->colorAllocate(255,210,185);
Example:
$apricot = $myImage->colorClosest(255,200,180);
If no colors have yet been allocated, then this call returns -1.
Example:
$mostred = $myImage->colorClosestHWB(255,0,0);
$rosey = $myImage->colorExact(255,100,80);
warn "Everything's coming up roses.\n" if $rosey >= 0;
$rosey = $myImage->colorResolve(255,100,80);
warn "Everything's coming up roses.\n" if $rosey >= 0;
$maxColors = $myImage->colorsTotal;
rgb()
to obtain the rgb color underneath the pixel.
Example:
$index = $myImage->getPixel(20,100);
($r,$g,$b) = $myImage->rgb($index);
Example:
@RGB = $myImage->rgb($peachy);
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;
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.
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->colorAllocate(255,255,255);
$black = $diagonal_brush->colorAllocate(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);
setThickness() to change the line drawing
width.
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.
setTile in order to define the particular tile pattern you'll use
for drawing when you specify the gdTiled color.
details.
setStyled() command.
gdAntiAliased color is used for drawing lines with antialiasing
turned on. Antialiasing will blend the jagged edges of lines with the
background, creating a smoother look. The actual color drawn is set
with setAntiAliased().
line() and polygon, will draw
antialiased lines if the special ``color'' gdAntiAliased is used when
calling them.
setAntiAliased() is used to specify the actual foreground color to be
used when drawing antialiased lines. You may set any color to be the
foreground, however as of libgd version 2.0.12 an alpha channel component is
not supported.
Antialiased lines can be drawn on both truecolor and palette-based images. However, attempts to draw antialiased lines on highly complex palette-based backgrounds may not give satisfactory results, due to the limited number of colors available in the palette. Antialiased line-drawing on simple backgrounds should work well with palette-based images; otherwise create or fetch a truecolor image instead.
setAntiAliasedDontBlend() method can be used to
indicate the special color that the foreground should stand out more
clearly against.
Once turned on, you can turn this feature off by calling
setAntiAliasedDontBlend() with a second argument of 0:
$image->setAntiAliasedDontBlend($color,0);
These methods allow you to draw lines, rectangles, and elipses, as well as to perform various special operations like flood-fill.
Example:
# This assumes $peach already allocated
$myImage->setPixel(50,50,$peach);
Example:
# Draw a diagonal line using the currently defind
# paintbrush pattern.
$myImage->line(0,0,150,150,gdBrushed);
setStyle() method described below and to draw with
the special color gdStyled.
Example:
$myImage->dashedLine(0,0,150,150,$blue);
Example:
$myImage->rectangle(10,10,100,100,$rose);
Example:
# read in a fill pattern and set it
$tile = newFromPng GD::Image('happyface.png');
$myImage->setTile($tile);
# draw the rectangle, filling it with the pattern
$myImage->filledRectangle(10,10,150,200,gdTiled);
Example:
$poly = new GD::Polygon;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
$myImage->polygon($poly,$blue);
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,$peachpuff);
methods() draw ellipses. ($cx,$cy) is the center of the arc, and
($width,$height) specify the ellipse width and height, respectively.
filledEllipse() is like Ellipse() except that the former produces
filled versions of the ellipse.
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);
arc() except that it colors in the pie wedge with
the selected color. $arc_style is optional. If present it is a
bitwise OR of the following constants:
gdArc connect start & end points of arc with a rounded edge gdChord connect start & end points of arc with a straight line gdPie synonym for gdChord gdNoFill outline the arc or chord gdEdged connect beginning and ending of the arc to the center
gdArc and gdChord are mutally exclusive. gdChord just connects the starting and ending angles with a straight line, while gdArc produces a rounded edge. gdPie is a synonym for gdArc. gdNoFill indicates that the arc or chord should be outlined, not filled. gdEdged, used together with gdNoFill, indicates that the beginning and ending angles should be connected to the center; this is a good way to outline (rather than fill) a ``pie slice.''
Example:
$image->filledArc(100,100,50,50,0,90,$blue,gdEdged|gdNoFill);
Example:
# Draw a rectangle, and then make its interior blue
$myImage->rectangle(10,10,100,100,$black);
$myImage->fill(50,50,$blue);
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.
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);
Example:
$myImage = new GD::Image(100,100);
... various drawing stuff ...
$copy = $myImage->clone;
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);
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.
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:
$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);
This method is similar to copyResized() but provides ``smooth'' copying
from a large image to a smaller one, using a weighted average of the
pixels of the source area rather than selecting one representative
pixel. This method is identical to copyResized() when the destination
image is a palette image.
Gd also provides some common image transformations:
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.
Example:
$myImage->string(gdSmallFont,2,10,"Peachy Keen",$peach);
The arguments are as follows:
fgcolor Color index to draw the string in fontname An absolute 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 FT 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.
Using a negative color index will disable anti-aliasing, as described in the libgd manual page at http://www.boutell.com/gd/manual2.0.9.html#gdImageStringFT.
An optional 8th argument allows you to pass a hashref of options to stringFT(). Two hashkeys are recognized: linespacing, if present, controls the spacing between lines of text. charmap, if present, sets the character map to use.
The value of linespacing is supposed to be a multiple of the character height, so setting linespacing to 2.0 will result in double-spaced lines of text. However the current version of libgd (2.0.12) does not do this. Instead the linespacing seems to be double what is provided in this argument. So use a spacing of 0.5 to get separation of exactly one line of text. In practice, a spacing of 0.6 seems to give nice results. Another thing to watch out for is that successive lines of text should be separated by the ``\r\n'' characters, not just ``\n''.
The value of charmap is one of ``Unicode'', ``Shift_JIS'' and ``Big5''. The interaction between Perl, Unicode and libgd is not clear to me, and you should experiment a bit if you want to use this feature.
Example:
$gd->stringFT($black,'/dosc/windows/Fonts/pala.ttf',40,0,20,90,
"hi there\r\nbye now",
{linespacing=>0.6,
charmap => 'Unicode',
});
For backward compatibility with older versions of the FreeType
library, the alias stringTTF() is also recognized. Also be aware that
relative font paths are not recognized due to problems in the libgd
library.
The alpha channel methods allow you to control the way drawings are processed according to the alpha channel. When true color is turned on, colors are encoded as four bytes, in which the last three bytes are the RGB color values, and the first byte is the alpha channel. Therefore the hexadecimal representation of a non transparent RGB color will be: C=0x00(rr)(bb)(bb)
When alpha blending is turned on, you can use the first byte of the
color to control the transparency, meaning that a rectangle painted
with color 0x00(rr)(bb)(bb) will be opaque, and another one painted
with 0x7f(rr)(gg)(bb) will be transparent. The Alpha value must be >=
0 and <= 0x7f.
alphaBlending() method allows for two different modes of drawing
on truecolor images. In blending mode, which is on by default (libgd
2.0.2 and above), the alpha channel component of the color supplied to
all drawing functions, such as setPixel, determines how much of the
underlying color should be allowed to shine through. As a result, GD
automatically blends the existing color at that point with the drawing
color, and stores the result in the image. The resulting pixel is
opaque. In non-blending mode, the drawing color is copied literally
with its alpha channel information, replacing the destination
pixel. Blending mode is not available when drawing on palette images.
saveAlpha(1) to turn on saving of such information, and call
alphaBlending(0) to turn off alpha blending within the library so
that alpha channel information is actually stored in the image rather
than being composited immediately at the time that drawing functions
are invoked.
These are various utility methods that are useful in some circumstances.
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 GD_CMP_TRUECOLOR The two images are not both true color
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($image2) & GD_CMP_IMAGE) {
warn "images differ!";
}
clip() with the coordinates of
the new clipping rectangle. Calling clip() without any arguments will
return the current clipping rectangle.
boundsSafe() method will return true if the point indicated by
($x,$y) is within the clipping rectangle, or false if it is not. If
the clipping rectangle has not been set, then it will return true if
the point lies within the image boundaries.
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). Also see the GD::Polyline manpage.
$poly = new GD::Polygon;
$poly->addPt(0,0);
$poly->addPt(0,50);
$poly->addPt(25,25);
$myImage->fillPoly($poly,$blue);
($x,$y) = $poly->getPt(2);
$poly->setPt(2,100,100);
($x,$y) = $poly->deletePt(1);
$poly->addPt(0,0);
$poly->toPt(0,50);
$poly->toPt(25,-25);
$myImage->fillPoly($poly,$blue);
$points = $poly->length;
@vertices = $poly->vertices;
foreach $v (@vertices)
print join(",",@$v),"\n";
}
($left,$top,$right,$bottom) = $poly->bounds;
$poly->offset(10,30);
# Make the polygon really tall
$poly->map($poly->bounds,0,0,50,200);
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.
Please see the GD::Polyline manpage for information on creating open polygons and splines.
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 stringFT() 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.
Each of these fonts is available both as an imported global (e.g. gdSmallFont) and as a package method (e.g. GD::Font->Small).
print "The large font contains ",gdLargeFont->nchars," characters\n";
height($w,$h) = (gdLargeFont->width,gdLargeFont->height);
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.
The GD.pm interface is copyright 1995-2000, 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