GD(3)

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 GIF and print it on standard output
    print $im->gif;

    # Convert the image to PNG and print it on standard output
    print $im->png;

DESCRIPTION
GD.pm is a patched version of the 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.

The patches reintroduce GIF support.

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 GIF and print it on standard output
        print $im->gif;

        # 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 GIF, PNG, GD, GD2 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.

Object Constructors: Creating Images
The following class methods allow you to create new GD::Image objects.

$image = GD::Image->new([$width,$height])
$image = GD::Image->new(*FILEHANDLE)
$image = GD::Image->new($filename)
$image = GD::Image->new($data)
    The 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.

    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 GIF, 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.

$image = GD::Image->newFromPng($file)
$image = GD::Image->newFromPngData($data)
    The 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.

    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.

$image = GD::Image->newFromJpeg($file)
$image = GD::Image->newFromJpegData($data)
    These methods will create an image from a JPEG file. They work just like newFromPng() and newFromPngData(), and will accept the same filehandle and pathname arguments.

    Bear in mind that JPEG is a 24-bit format, while GD is 8-bit. This means that photographic images will become posterized.

$image = GD::Image->newFromXbm($file)
    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;

    There is no newFromXbmData() function, because there is no corresponding function in the gd library.

$image = GD::Image->newFromWMP($file)
    This creates a new GD::Image object starting from a WBMP-format file or filehandle. There is currently no newFromWMPData() method.

$image = GD::Image->newFromGd($file)
$image = GD::Image->newFromGdData($data)
    These methods initialize a GD::Image from a Gd file, filehandle, or data. 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.

            $myImage = newFromGd GD::Image("godzilla.gd") || die;
            close GDF;

$image = GD::Image->newFromGd2($file)
$image = GD::Image->newFromGd2Data($data)
    This works in exactly the same way as "newFromGd()" and newFromGdData, but use the new compressed GD2 image format.

$image = GD::Image->newFromGd2Part($file,srcX,srcY,width,height)
    This class method allows you to read in just a portion of a GD2 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).

$image = GD::Image->newFromGif($file)
$image = GD::Image->newFromGifData($data)
    This works in exactly the same way as "newFromGd()" and newFromGdData, but use the GIF image format.

$image = GD::Image->newFromXpm($filename)
    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: The libgd library is unable to read certain XPM files, returning an all-black image instead.

GD::Image Methods
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.

$pngdata = $image->png
    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.

$gifdata = $image->gif
    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.

$jpegdata = $image->jpeg([$quality])
    This returns the image data in JPEG format. You can then print it, pipe it to a display program, or write it to a file. You may pass an optional quality score to 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.

$gddata = $image->gd
    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;

$gd2data = $image->gd2
    Same as gd(), except that it returns the data in compressed GD2 format.

$wbmpdata = $image->wbmp([$foreground])
    This returns the image data in WBMP format, which is a black-and-white image format. Provide the index of the color to become the foreground color. All other pixels will be considered background. These methods allow you to control and manipulate the GD::Image color table.

$index = $image->colorAllocate(red,green,blue)
    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);

$image->colorDeallocate(colorIndex)
    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);

$index = $image->colorClosest(red,green,blue)
    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);

$index = $image->colorClosestHWB(red,green,blue)
    This also attempts to return the color closest in the color table to the red green and blue components specified. If uses a Hue/White/Black color representation to make the selected colour more likely to match human perceptions of similar colors.

    If no colors have yet been allocated, then this call returns -1.

    Example:

            $mostred = $myImage->colorClosestHWB(255,0,0);

$index = $image->colorExact(red,green,blue)
    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;

$index = $image->colorResolve(red,green,blue)
    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;

$index = $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);

($red,$green,$blue) = $image->rgb($index)
    This returns a list containing the red, green and blue components of the specified color index.

    Example:

            @RGB = $myImage->rgb($peachy);

$image->transparent($colorIndex)
    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 & 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;
    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.

$image->setBrush($image)
    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);

$image->setStyle(@colors)
    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. These methods allow you to draw lines, rectangles, and elipses, as well as to perform various special operations like flood-fill.

$image->setPixel($x,$y,$color)
    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);

$image->line($x1,$y1,$x2,$y2,$color)
    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);

$image->dashedLine($x1,$y1,$x2,$y2,$color)
    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);

GD::Image::rectangle($x1,$y1,$x2,$y2,$color)
    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);

$image->filledRectangle($x1,$y1,$x2,$y2,$color)
    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
            $tile = newFromPng GD::Image('happyface.png');
            $myImage->setTile($tile);

            # draw the rectangle, filling it with the pattern
            $myImage->filledRectangle(10,10,150,200,gdTiled);

$image->polygon($polygon,$color)
    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);

$image->filledPolygon($poly,$color)
    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);

$image->arc($cx,$cy,$width,$height,$start,$end,$color)
    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);

$image->fill($x,$y,$color)
    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)
    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.

$image->copy($sourceImage,$dstX,$dstY,$srcX,$srcY,$width,$height)
    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);

$image->clone()
    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)
    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)
    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.

$image->copyResized($sourceImage,$dstX,$dstY,$srcX,$srcY,$destW,$destH,$srcW,$srcH)
    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);
    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.

$image->string($font,$x,$y,$string,$color)
    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);

$image->stringUp($font,$x,$y,$string,$color)
    Just like the previous call, but draws the text rotated counterclockwise 90 degrees.

$image->char($font,$x,$y,$char,$color)
$image->charUp($font,$x,$y,$char,$color)
    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.

@bounds = $image->stringFT($fgcolor,$fontname,$ptsize,$angle,$x,$y,$string)
@bounds = GD::Image->stringFT($fgcolor,$fontname,$ptsize,$angle,$x,$y,$string)
    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 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.

    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. These are various utility methods that are useful in some circumstances.

$image->interlaced([$flag])
    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.

($width,$height) = $image->getBounds()
    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.

$flag = $image1->compare($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!";
      }

Polygons
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).

$poly = GD::Polygon->new
    Create an empty polygon with no vertices.

            $poly = new GD::Polygon;

$poly->addPt($x,$y)
    Add point (x,y) to the polygon.

            $poly->addPt(0,0);
            $poly->addPt(0,50);
            $poly->addPt(25,25);
            $myImage->fillPoly($poly,$blue);

($x,$y) = $poly->getPt($index)
    Retrieve the point at the specified vertex.

            ($x,$y) = $poly->getPt(2);

$poly->setPt($index,$x,$y)
    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);

($x,$y) = $poly->deletePt($index)
    Delete the specified vertex, returning its value.

            ($x,$y) = $poly->deletePt(1);

$poly->toPt($dx,$dy)
    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);

$vertex_count = $poly->length
    Return the number of vertices in the polygon.

            $points = $poly->length;

@vertices = $poly->vertices
    Return a list of all the verticies in the polygon object. Each member of the list is a reference to an (x,y) array.

            @vertices = $poly->vertices;
            foreach $v (@vertices)
               print join(",",@$v),"\n";
            }

@rect = $poly->bounds
    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;

$poly->offset($dx,$dy)
    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);

$poly->map($srcL,$srcT,$srcR,$srcB,$destL,$dstT,$dstR,$dstB)
    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);

$poly->scale($sx,$sy)
    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.

$poly->transform($sx,$rx,$sy,$ry,$tx,$ty)
    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 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).

gdSmallFont
GD::Font->Small
    This is the basic small font, "borrowed" from a well known public domain 6x12 font.

gdLargeFont
GD::Font->Large
    This is the basic large font, "borrowed" from a well known public domain 8x16 font.

gdMediumBoldFont
GD::Font->MediumBold
    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
    This is a tiny, almost unreadable font, 5x8 pixels wide.

gdGiantFont
GD::Font->Giant
    This is a 9x15 bold font converted by Jan Pazdziora from a sans serif X11 font.

$font->nchars
    This returns the number of characters in the font.

            print "The large font contains ",gdLargeFont->nchars," characters\n";

$font->offset
    This returns the ASCII value of the first character in the font

$width = $font->width
$height = $font->height
"height"
    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.

AUTHOR
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

SEE ALSO
Image::Magick