Image Data Output Methods

The following methods convert the internal drawing format into standard output file formats.

$pngdata = $image->png([$compression_level])

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.

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).

$gifdata = $image->gifanimbegin([$GlobalCM [, $Loops]])

For libgd version 2.0.33 and higher, this call begins an animated GIF by returning the data that comprises animated gif image file header. After you call this method, call gifanimadd() one or more times to add the frames of the image. Then call gifanimend(). Each frame must be the same width and height.

A typical sequence will look like this:

my $gifdata = $image->gifanimbegin;
$gifdata   .= $image->gifanimadd;    # first frame
for (1..100) {
   # make a frame of right size
   my $frame  = GD::Image->new($image->getBounds);
   add_frame_data($frame);              # add the data for this frame
   $gifdata   .= $frame->gifanimadd;     # add frame
}
$gifdata   .= $image->gifanimend;   # finish the animated GIF
print $gifdata;                     # write animated gif to STDOUT

If you do not wish to store the data in memory, you can print it to stdout or a file.

The image that you call gifanimbegin on is used to set the image size, color resolution and color map. If argument $GlobalCM is 1, the image color map becomes the GIF89a global color map. If $Loops is given and >= 0, the NETSCAPE2.0 application extension is created, with looping count. Looping count 0 means forever.

$gifdata = $image->gifanimadd([$LocalCM [, $LeftOfs [, $TopOfs [, $Delay [, $Disposal [, $previm]]]]]])

Returns the data that comprises one animated gif image frame. You can then print it, pipe it to a display program, or write it to a file. With $LeftOfs and $TopOfs you can place this frame in different offset than (0,0) inside the image screen. Delay between the previous frame and this frame is in 1/100s units. Disposal is usually and by default 1. Compression is activated by giving the previous image as a parameter. This function then compares the images and only writes the changed pixels to the new frame in animation. The Disposal parameter for optimized animations must be set to 1, also for the first frame. $LeftOfs and $TopOfs parameters are ignored for optimized frames.

$gifdata = $image->gifanimend()

Returns the data for end segment of animated gif file. It always returns string ';'. This string must be printed to an animated gif file after all image frames to properly terminate it according to GIF file syntax. Image object is not used at all in this method.

$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.

$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.

$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.

$bmpdata = $image->bmp([$compression])

This returns the image data in BMP format, which is a Windows Bitmap. If compression is set to 1, it will use RLE compression on the pixel data; otherwise, setting it to 0 (the default) will leave the BMP pixel data uncompressed.

$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.

$tiffdata = $image->tiff()

This returns the image data in TIFF format.

$webpdata = $image->webp([$quality])

This returns the image data in WEBP format, with the optional quality argument. The default is 80, also chosen by the value -1. A quality value of >= 101 is considered Lossless.

$webpdata = $image->heif([$quality])

This returns the truecolor image data in HEIF format, with the optional quality and speed arguments. If truecolor is not set, this fails. The default quality is 80, also chosen by the value -1. A quality value of 200 is considered Lossless.

$webpdata = $image->avif([$quality,$speed])

This returns the truecolor image data in AVIF format, with the AVif encoder and 444 chroma, and the optional quality argument. If truecolor is not set, this fails. The default compression quality 1-100 is -1, the default speed 0-10 is 6.

$success = $image->_file($filename)

Writes an image to a file in the format indicated by the filename, with libgd versions >= gd-2.1.1.

File type is determined by the extension of the file name. See "supportsFiletype" for an overview of the parsing.

For file types that require extra arguments, "_file" attempts to use sane defaults:

C<gdImageGd2> chunk size = 0, compression is enabled.
C<gdImageJpeg>        quality = -1 (i.e. the reasonable default)
C<gdImageWBMP>        foreground is the darkest available color
C<gdImageWEBP>        quality default
C<gdImageHEIF>        quality default, codes = HEVC, chroma = 444
C<gdImageAVIF>        quality default, speed = 6

Everything else is called with the two-argument function and so will use the default values.

"_file" and the underlying libgd "gdImageFile" has some rudimentary error detection and will return FALSE (0) if a detectable error occurred. However, the image loaders do not normally return their error status so a result of TRUE (1) does **not** mean the file was saved successfully.

Color Control

These methods allow you to control and manipulate the GD::Image color table for palette, non-truecolor images.

$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:

$black = $myImage->colorAllocate(0,0,0); #background color
$white = $myImage->colorAllocate(255,255,255);
$peachpuff = $myImage->colorAllocate(255,218,185);

$index = $image->colorAllocateAlpha(reg,green,blue,alpha)

This allocates a color with the specified red, green, and blue components, plus the specified alpha channel. The alpha value may range from 0 (opaque) to 127 (transparent). The "alphaBlending" function changes the way this alpha channel affects the resulting image.

$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->colorClosestAlpha(red,green,blue,alpha)

This returns the index of the color closest in the color table to the red green blue and alpha components specified. If no colors have yet been allocated, then this call returns -1.

Example:

$apricot = $myImage->colorClosestAlpha(255,200,180,0);

$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. It uses a Hue/White/Black color representation to make the selected color 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->colorExactAlpha(red,green,blue,alpha)

This returns the index of a color that exactly matches the specified red green blue and alpha components. If such a color is not in the color table, this call returns -1.

$rosey = $myImage->colorExactAlpha(255,100,80,0);
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;

$index = $image->colorResolveAlpha(red,green,blue,alpha)

This returns the index of a color that exactly matches the specified red green blue and alpha 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->colorResolveAlpha(255,100,80,0);
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;

In the case of a TrueColor image, this call will return undef.

$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);

($alpha) = $image->alpha($index)

This returns an item containing the alpha component 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 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 = GD::Image->newFromPng(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.

$image->setBrush($image)

You can draw lines and shapes using a brush pattern. Brushes are just palette, not TrueColor, 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 = GD::Image->new(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);

$image->setThickness($thickness)

Lines drawn with line(), rectangle(), arc(), and so forth are 1 pixel thick by default. Call setThickness() to change the line drawing width.

$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.

gdAntiAliased

The "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().

$image->setAntiAliased($color)

"Antialiasing" is a process by which jagged edges associated with line drawing can be reduced by blending the foreground color with an appropriate percentage of the background, depending on how much of the pixel in question is actually within the boundaries of the line being drawn. All line-drawing methods, such as 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. When using palette-based images, be sure to allocate a broad spectrum of colors in order to have sufficient colors for the antialiasing to use.

$image->setAntiAliasedDontBlend($color,[$flag])

Normally, when drawing lines with the special gdAntiAliased "color," blending with the background to reduce jagged edges is the desired behavior. However, when it is desired that lines not be blended with one particular color when it is encountered in the background, the 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);

Drawing Commands

These methods allow you to draw lines, rectangles, and ellipses, 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 defined
# paintbrush pattern.
$myImage->line(0,0,150,150,gdBrushed);

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

DEPRECATED: The libgd library provides this method solely for backward compatibility with libgd version 1.0, and there have been reports that it no longer works as expected. Please use the setStyle() and gdStyled methods as described below.

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);

$image->rectangle($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) =item $image->setTile($otherimage)

This draws a rectangle 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:

# read in a fill pattern and set it
$tile = GD::Image->newFromPng('happyface.png');
$myImage->setTile($tile); 
# draw the rectangle, filling it with the pattern
$myImage->filledRectangle(10,10,150,200,gdTiled);

$image->openPolygon($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 = GD::Polygon->new;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
$myImage->openPolygon($poly,$blue);

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

This draws a sequence of connected lines with the specified color, without connecting the first and last point to a closed polygon. The polygon must be created first (see below). The polygon must have at least three vertices. Both real color indexes and the special colors gdBrushed, gdStyled and gdStyledBrushed can be specified.

You need libgd 2.0.33 or higher to use this feature.

Example:

$poly = GD::Polygon->new;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
$myImage->unclosedPolygon($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 = GD::Polygon->new;
$poly->addPt(50,0);
$poly->addPt(99,99);
$poly->addPt(0,99);
# draw the polygon, filling it with a color
$myImage->filledPolygon($poly,$peachpuff);

$image->ellipse($cx,$cy,$width,$height,$color)

$image->filledEllipse($cx,$cy,$width,$height,$color)

These 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.

$image->arc($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 right end 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);

$image->filledArc($cx,$cy,$width,$height,$start,$end,$color [,$arc_style])

This method is like 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 mutually 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);

$image->fill($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);

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.

$image->copy($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 = GD::Image->new(100,100);
... various drawing stuff ...
$srcImage = GD::Image->new(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 = GD::Image->new(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 = GD::Image->new(100,100);
... various drawing stuff ...
$redImage = GD::Image->new(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 accommodate the size requirements.

Example:

$myImage = GD::Image->new(100,100);
... various drawing stuff ...
$srcImage = GD::Image->new(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);

$image->copyResampled($sourceImage,$dstX,$dstY,

$srcX,$srcY,$destW,$destH,$srcW,$srcH)

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.

$image->copyRotated($sourceImage,$dstX,$dstY,

$srcX,$srcY,$width,$height,$angle)

Like copyResized() but the $angle argument specifies an arbitrary amount to rotate the image counter clockwise (in degrees). In addition, $dstX and $dstY species the center of the destination image, and not the top left corner.

$image->trueColorToPalette([$dither], [$colors])

This method converts a truecolor image to a palette image. The code for this function was originally drawn from the Independent JPEG Group library code, which is excellent. The code has been modified to preserve as much alpha channel information as possible in the resulting palette, in addition to preserving colors as well as possible. This does not work as well as might be hoped. It is usually best to simply produce a truecolor output image instead, which guarantees the highest output quality. Both the dithering (0/1, default=0) and maximum number of colors used (<=256, default = gdMaxColors) can be specified.

$image = $sourceImage->createPaletteFromTrueColor([$dither], [$colors])

Creates a new palette image from a truecolor image. Same as above, but returns a new image.

Don't use these function -- write real truecolor PNGs and JPEGs. The disk space gain of conversion to palette is not great (for small images it can be negative) and the quality loss is ugly.

$error = $image->colorMatch($otherimage)

Bring the palette colors in $otherimage to be closer to truecolor $image. A negative return value is a failure.

-1 image must be True Color
-2 otherimage must be indexed
-3 the images are meant to be the same dimensions
-4 At least 1 color in otherimage must be allocated

This method is only available with libgd >= 2.1.0

$image = $sourceImage->neuQuant($maxcolor=256,$samplefactor=5)

Creates a new palette image from a truecolor image.

Image Transformation Commands

Gd provides these simple image transformations, non-interpolated.

$image = $sourceImage->copyRotate90()

$image = $sourceImage->copyRotate180()

$image = $sourceImage->copyRotate270()

$image = $sourceImage->copyFlipHorizontal()

$image = $sourceImage->copyFlipVertical()

$image = $sourceImage->copyTranspose()

$image = $sourceImage->copyReverseTranspose()

These methods can be used to rotate, flip, or transpose an image. The result of the method is a copy of the image.

$image->rotate180()

$image->flipHorizontal()

$image->flipVertical()

These methods are similar to the copy* versions, but instead modify the image in place.

Image Interpolation Methods

Since libgd 2.1.0 there are better transformation methods, with these interpolation methods:

GD_BELL                - Bell
GD_BESSEL              - Bessel
GD_BILINEAR_FIXED      - fixed point bilinear
GD_BICUBIC             - Bicubic
GD_BICUBIC_FIXED       - fixed point bicubic integer
GD_BLACKMAN            - Blackman
GD_BOX                 - Box
GD_BSPLINE             - BSpline
GD_CATMULLROM          - Catmullrom
GD_GAUSSIAN            - Gaussian
GD_GENERALIZED_CUBIC   - Generalized cubic
GD_HERMITE             - Hermite
GD_HAMMING             - Hamming
GD_HANNING             - Hannig
GD_MITCHELL            - Mitchell
GD_NEAREST_NEIGHBOUR   - Nearest neighbour interpolation
GD_POWER               - Power
GD_QUADRATIC           - Quadratic
GD_SINC                - Sinc
GD_TRIANGLE            - Triangle
GD_WEIGHTED4           - 4 pixels weighted bilinear interpolation
GD_LINEAR              - bilinear interpolation

$image->interpolationMethod( [$method] )

Gets or sets the interpolation methods for all subsequent interpolations. See above for the valid values. Only available since libgd 2.2.0

$image->copyScaleInterpolated( width, height )

Returns a copy, using interpolation.

$image->copyRotateInterpolated( angle, bgcolor )

Returns a copy, using interpolation.

Image Filter Commands

Gd also provides some common image filters, they modify the image in place and return TRUE if modified or FALSE if not. Most of them need libgd >= 2.1.0, with older versions those functions are undefined.

$ok = $image->scatter($sub, $plus)

if $sub and $plus are 0, nothing is changed, TRUE is returned. if $sub >= $plus, nothing is changed, FALSE is returned. else random pixels are changed.

$ok = $image->scatterColor($sub, $plus, @colors)

Similar to scatter, but using the given array of colors, i.e. palette indices.

$ok = $image->pixelate($blocksize, $mode)

if $blocksize <= 0, nothing is changed, FALSE is returned. if $blocksize == 1, nothing is changed, TRUE is returned. else the following modes are observed:
GD_PIXELATE_UPPERLEFT
GD_PIXELATE_AVERAGE

$ok = $image->negate()

$ok = $image->grayscale()

$ok = $image->brightness($add)

$add: -255..255

$ok = $image->contrast($contrast)

$contrast: a double value. The contrast adjustment value. Negative values increase, positive values decrease the contrast. The larger the absolute value, the stronger the effect.

$ok = $image->color($red,$green,$blue,$alpha)

Change channel values of an image.

$red   - The value to add to the red channel of all pixels.
$green - The value to add to the green channel of all pixels.
$blue  - The value to add to the blue channel of all pixels.
$alpha - The value to add to the alpha channel of all pixels.

$ok = $image->selectiveBlur()

$ok = $image->edgeDetectQuick()

$ok = $image->gaussianBlur()

$ok = $image->emboss()

$ok = $image->meanRemoval()

$ok = $image->smooth($weight)

$image = $sourceImage->copyGaussianBlurred($radius, $sigma)

$radius: int, the blur radius (*not* diameter--range is 2*radius + 1) a radius, not a diameter so a radius of 2 (for example) will blur across a region 5 pixels across (2 to the center, 1 for the center itself and another 2 to the other edge).

$sigma: the sigma value or a value <= 0.0 to use the computed default. represents the "fatness" of the curve (lower == fatter).

The result is always truecolor.

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 monospaced fonts, available in the global variables gdGiantFont, gdLargeFont, gdMediumBoldFont, gdSmallFont and gdTinyFont.

In addition, you can use the load() method to load GD-formatted bitmap font files at runtime. You can create these bitmap files from X11 BDF-format files using the bdf2gd.pl script, which should have been installed with GD (see the bdf_scripts directory if it wasn't). The format happens to be identical to the old-style MSDOS bitmap ".fnt" files, so you can use one of those directly if you happen to have one.

For writing proportional scalable fonts, GD offers the stringFT() method, which allows you to load and render any TrueType font on your system.

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

This method draws a string starting 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.

$font = GD::Font->load($fontfilepath)

This method dynamically loads a font file, returning a font that you can use in subsequent calls to drawing methods. For example:

my $courier = GD::Font->load('./courierR12.fnt') or die "Can't load font";
$image->string($courier,2,10,"Peachy Keen",$peach);

Font files must be in GD binary format, as described above.

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

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

@bounds = $image->stringFT($fgcolor,$fontname,$ptsize,$angle,$x,$y,$string,\%options)

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   A path to the TrueType (.ttf) font file or a font pattern.
ptsize     The desired point size (may be fractional)
angle      The rotation angle, in radians (positive values rotate counter clockwise)
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.

The fontname argument is the name of the font, which can be a full pathname to a .ttf file, or if not the paths in $ENV{GDFONTPATH} will be searched or if empty the libgd compiled DEFAULT_FONTPATH. The TrueType extensions .ttf, .pfa, .pfb or .dfont can be omitted.

The string may contain UTF-8 sequences like: "&#192;"

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 antialiasing, as described in the libgd manual page at https://libgd.github.io/manuals/2.0.35/#gdImageStringFT.

An optional 8th argument allows you to pass a hashref of options to stringFT(). Several hashkeys are recognized: linespacing, charmap, resolution, and kerning.

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.

The value of resolution is the vertical and horizontal resolution, in DPI, in the format "hdpi,vdpi". If present, the resolution will be passed to the Freetype rendering engine as a hint to improve the appearance of the rendered font.

The value of kerning is a flag. Set it to false to turn off the default kerning of text.

Example:

$gd->stringFT($black,'/c/windows/Fonts/pala.ttf',40,0,20,90,
             "hi there\r\nbye now",
             {linespacing=>0.6,
              charmap  => 'Unicode',
             });

If GD was compiled with fontconfig support, and the fontconfig library is available on your system, then you can use a font name pattern instead of a path. Patterns are described in fontconfig and will look something like this "Times:italic". For backward compatibility, this feature is disabled by default. You must enable it by calling useFontConfig(1) prior to the stringFT() call.

$image->useFontConfig(1);

For backward compatibility with older versions of the FreeType library, the alias stringTTF() is also recognized.

$hasfontconfig = $image->useFontConfig($flag)

Call useFontConfig() with a value of 1 in order to enable support for fontconfig font patterns (see stringFT). Regardless of the value of $flag, this method will return a true value if the fontconfig library is present, or false otherwise.

This method can also be called as a class method of GD::Image;

$result = $image->stringFTCircle($cx,$cy,$radius,$textRadius,$fillPortion,$font,$points,$top,$bottom,$fgcolor)

This draws text in a circle. Currently (libgd 2.0.33) this function does not work for me, but the interface is provided for completeness. The call signature is somewhat complex. Here is an excerpt from the libgd manual page:

Draws the text strings specified by top and bottom on the image, curved along the edge of a circle of radius radius, with its center at cx and cy. top is written clockwise along the top; bottom is written counterclockwise along the bottom. textRadius determines the "height" of each character; if textRadius is 1/2 of radius, characters extend halfway from the edge to the center. fillPortion varies from 0 to 1.0, with useful values from about 0.4 to 0.9, and determines how much of the 180 degrees of arc assigned to each section of text is actually occupied by text; 0.9 looks better than 1.0 which is rather crowded. font is a freetype font; see gdImageStringFT. points is passed to the freetype engine and has an effect on hinting; although the size of the text is determined by radius, textRadius, and fillPortion, you should pass a point size that "hints" appropriately -- if you know the text will be large, pass a large point size such as 24.0 to get the best results. fgcolor can be any color, and may have an alpha component, do blending, etc.

Returns a true value on success.

Alpha channels

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.

$image->alphaBlending($integer)

The 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.

Pass a value of 1 for blending mode, and 0 for non-blending mode.

$image->saveAlpha($saveAlpha)

By default, GD (libgd 2.0.2 and above) does not attempt to save full alpha channel information (as opposed to single-color transparency) when saving PNG images. (PNG is currently the only output format supported by gd which can accommodate alpha channel information.) This saves space in the output file. If you wish to create an image with alpha channel information for use with tools that support it, call 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.

Miscellaneous Image Methods

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 change the size of the image once it's created.

$width = $image->width

$height = $image->height

Return the width and height of the image, respectively.

$is_truecolor = $image->isTrueColor()

This method will return a Boolean representing whether the image is true color or not.

$flag = $image1->compare($image2)

Compare two images and return a bitmap describing the differences found, if any. The return value must be logically AND'ed 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
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!";
}

$image->clip($x1,$y1,$x2,$y2)

($x1,$y1,$x2,$y2) = $image->clip

Set or get the clipping rectangle. When the clipping rectangle is set, all drawing will be clipped to occur within this rectangle. The clipping rectangle is initially set to be equal to the boundaries of the whole image. Change it by calling clip() with the coordinates of the new clipping rectangle. Calling clip() without any arguments will return the current clipping rectangle.

$flag = $image->boundsSafe($x,$y)

The 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.

Grouping Methods

GD does not support grouping of objects, but GD::SVG does. In that subclass, the following methods declare new groups of graphical objects:

$image->startGroup([$id,\%style])

$image->endGroup()

$group = $image->newGroup

See GD::SVG for information.

GD::Polyline

Please see GD::Polyline for information on creating open polygons and splines.