LXV. Image Functions

Introduction

PHP is not limited to creating just HTML output. It can also be used to create and manipulate image files in a variety of different image formats, including gif, png, jpg, wbmp, and xpm. Even more convenient, PHP can output image streams directly to a browser. You will need to compile PHP with the GD library of image functions for this to work. GD and PHP may also require other libraries, depending on which image formats you want to work with.

You can use the image functions in PHP to get the size of JPEG, GIF, PNG, SWF, TIFF and JPEG2000 images.

With the exif extension, you are able to work with information stored in headers of JPEG and TIFF images. This way you can read meta data generated by digital cameras. The exif functions do not require the GD library.

Note: Read the requirements section about how to expand image capabilities to read, write and modify images. To read meta data of pictures taken by digital cameras you need the above mentioned exif extension.

Requirements

If you have the GD library (available at http://www.libgd.org/) you will also be able to create and manipulate images.

The format of images you are able to manipulate depend on the version of GD you install, and any other libraries GD might need to access those image formats. Versions of GD older than gd-1.6 support GIF format images, and do not support PNG, where versions greater than gd-1.6 and less than gd-2.0.28 support PNG, not GIF. GIF support was re-enabled in gd-2.0.28.

Note: Since PHP 4.3 there is a bundled version of the GD lib. This bundled version has some additional features like alpha blending, and should be used in preference to the external library since its codebase is better maintained and more stable.

Note: Support for GD 1.x has been removed as of PHP 6.0.0, which requires GD 2.0.33 or later.

You may wish to enhance GD to handle more image formats.

Table 1. Supported image formats

Image format	Library to download	Notes
`gif`		Only supported in GD versions older than gd-1.6 and newer than gd-2.0.28. Read-only GIF support is available with PHP 4.3.0 and the bundled GD-library. Write support is available since PHP 4.3.9 and PHP 5.0.1.
`jpeg-6b`	ftp://ftp.uu.net/graphics/jpeg/	When buliding the jpeg-v6b library (prior to building PHP) you must use the `--enable-shared` option in the configure step. If you do not, you will receive an error saying `libjpeg.(a\|so) not found` when you get to the configure step of building PHP.
`png`	http://www.libpng.org/pub/png/libpng.html	Only supported in GD versions greater than gd-1.6.
`xpm`	ftp://metalab.unc.edu/pub/Linux/libs/X/!INDEX.html	It's likely you have this library already available, if your system has an installed X-Environment.

You may wish to enhance GD to deal with different fonts. The following font libraries are supported:

Table 2. Supported font libraries

Font library	Download	Notes
`FreeType 1.x`	http://www.freetype.org/	Support removed as of PHP 6.0.0
`FreeType 2`	http://www.freetype.org/
`T1lib`	ftp://sunsite.unc.edu/pub/Linux/libs/graphics/)	Support for Postscript Type 1 fonts.

Installation

To enable GD-support configure PHP --with-gd[=DIR], where DIR is the GD base install directory. To use the recommended bundled version of the GD library (which was first bundled in PHP 4.3.0), use the configure option --with-gd. GD library requires libpng and libjpeg to compile.

In Windows, you'll include the GD2 DLL php_gd2.dll as an extension in php.ini. The GD1 DLL php_gd.dll was removed in PHP 4.3.2. Also note that the preferred truecolor image functions, such as imagecreatetruecolor(), require GD2.

To disable GD support in PHP 3 add --without-gd to your configure line.

Enhance the capabilities of GD to handle more image formats by specifying the --with-XXXX configure switch to your PHP configure line.

Table 3. Supported image formats

Image Format	Configure Switch
`jpeg-6b`	To enable support for jpeg-6b add `--with-jpeg-dir=DIR`.
`png`	To enable support for png add `--with-png-dir=DIR`. Note, libpng requires the zlib library, therefore add `--with-zlib-dir[=DIR]` to your configure line.
`xpm`	To enable support for xpm add `--with-xpm-dir=DIR`. If configure is not able to find the required libraries, you may add the path to your X11 libraries.

Note: When compiling PHP with libpng, you must use the same version that was linked with the GD library.

Enhance the capabilities of GD to deal with different fonts by specifying the --with-XXXX configure switch to your PHP configure line.

Table 4. Supported font libraries

Font library	Configure Switch
`FreeType 1.x`	To enable support for FreeType 1.x add `--with-ttf[=DIR]`.
`FreeType 2`	To enable support for FreeType 2 add `--with-freetype-dir=DIR`.
`T1lib`	To enable support for T1lib (Postscript Type 1 fonts) add `--with-t1lib[=DIR]`.
`Native TrueType string function`	To enable support for native TrueType string function add `--enable-gd-native-ttf`.

Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

Table 5. Image Configure Options

Name	Default	Changeable	Changelog
gd.jpeg_ignore_warning	"0"	PHP_INI_ALL	Available since PHP 5.1.4.

For further details and definitions of the PHP_INI_* constants, see the Appendix I.

Here's a short explanation of the configuration directives.

gd.jpeg_ignore_warning bool: Ignore warnings created by jpeg2wbmp() and imagecreatefromjpeg()

See also the exif configuration directives.

Warning

Image functions are very memory intensive. Be sure to set memory_limit high enough.

Resource Types

This extension defines two resource types: an image identifier and a font identifier.

Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

IMG_GIF (integer)
IMG_JPG (integer)
IMG_JPEG (integer)
IMG_PNG (integer)
IMG_WBMP (integer)
IMG_XPM (integer)
IMG_COLOR_TILED (integer)
IMG_COLOR_STYLED (integer)
IMG_COLOR_BRUSHED (integer)
IMG_COLOR_STYLEDBRUSHED (integer)
IMG_COLOR_TRANSPARENT (integer)
IMG_ARC_ROUNDED (integer)
IMG_ARC_PIE (integer)
IMG_ARC_CHORD (integer)
IMG_ARC_NOFILL (integer)
IMG_ARC_EDGED (integer)
IMG_GD2_RAW (integer)
IMG_GD2_COMPRESSED (integer)
IMG_EFFECT_REPLACE (integer)
IMG_EFFECT_ALPHABLEND (integer)
IMG_EFFECT_NORMAL (integer)
IMG_EFFECT_OVERLAY (integer)
IMG_FILTER_NEGATE (integer)
IMG_FILTER_GRAYSCALE (integer)
IMG_FILTER_BRIGHTNESS (integer)
IMG_FILTER_CONTRAST (integer)
IMG_FILTER_COLORIZE (integer)
IMG_FILTER_EDGEDETECT (integer)
IMG_FILTER_GAUSSIAN_BLUR (integer)
IMG_FILTER_SELECTIVE_BLUR (integer)
IMG_FILTER_EMBOSS (integer)
IMG_FILTER_MEAN_REMOVAL (integer)
IMG_FILTER_SMOOTH (integer)
IMAGETYPE_GIF (integer)
IMAGETYPE_JPEG (integer)
IMAGETYPE_PNG (integer)
IMAGETYPE_SWF (integer)
IMAGETYPE_PSD (integer)
IMAGETYPE_BMP (integer)
IMAGETYPE_WBMP (integer)
IMAGETYPE_XBM (integer)
IMAGETYPE_TIFF_II (integer)
IMAGETYPE_TIFF_MM (integer)
IMAGETYPE_IFF (integer)
IMAGETYPE_JB2 (integer)
IMAGETYPE_JPC (integer)
IMAGETYPE_JP2 (integer)
IMAGETYPE_JPX (integer)
IMAGETYPE_SWC (integer)
PNG_NO_FILTER (integer)
PNG_FILTER_NONE (integer)
PNG_FILTER_SUB (integer)
PNG_FILTER_UP (integer)
PNG_FILTER_AVG (integer)
PNG_FILTER_PAETH (integer)
PNG_ALL_FILTERS (integer)

Examples

Example 1. PNG creation with PHP


<?php

header("Content-type: image/png");
$string = $_GET['text'];
$im     = imagecreatefrompng("images/button1.png");
$orange = imagecolorallocate($im, 220, 210, 60);
$px     = (imagesx($im) - 7.5 * strlen($string)) / 2;
imagestring($im, 3, $px, 9, $string, $orange);
imagepng($im);
imagedestroy($im);

?>

This example would be called from a page with a tag like: <img src="button.php?text=text">. The above button.php script then takes this "text" string and overlays it on top of a base image which in this case is "images/button1.png" and outputs the resulting image. This is a very convenient way to avoid having to draw new button images every time you want to change the text of a button. With this method they are dynamically generated.

Table of Contents
gd_info -- Retrieve information about the currently installed GD library
getimagesize -- Get the size of an image
image_type_to_extension -- Get file extension for image type
image_type_to_mime_type -- Get Mime-Type for image-type returned by getimagesize, exif_read_data, exif_thumbnail, exif_imagetype
image2wbmp -- Output image to browser or file
imagealphablending -- Set the blending mode for an image
imageantialias -- Should antialias functions be used or not
imagearc -- Draws an arc
imagechar -- Draw a character horizontally
imagecharup -- Draw a character vertically
imagecolorallocate -- Allocate a color for an image
imagecolorallocatealpha -- Allocate a color for an image
imagecolorat -- Get the index of the color of a pixel
imagecolorclosest -- Get the index of the closest color to the specified color
imagecolorclosestalpha -- Get the index of the closest color to the specified color + alpha
imagecolorclosesthwb -- Get the index of the color which has the hue, white and blackness nearest to the given color
imagecolordeallocate -- De-allocate a color for an image
imagecolorexact -- Get the index of the specified color
imagecolorexactalpha -- Get the index of the specified color + alpha
imagecolormatch -- Makes the colors of the palette version of an image more closely match the true color version
imagecolorresolve -- Get the index of the specified color or its closest possible alternative
imagecolorresolvealpha -- Get the index of the specified color + alpha or its closest possible alternative
imagecolorset -- Set the color for the specified palette index
imagecolorsforindex -- Get the colors for an index
imagecolorstotal -- Find out the number of colors in an image's palette
imagecolortransparent -- Define a color as transparent
imageconvolution -- Apply a 3x3 convolution matrix, using coefficient and offset
imagecopy -- Copy part of an image
imagecopymerge -- Copy and merge part of an image
imagecopymergegray -- Copy and merge part of an image with gray scale
imagecopyresampled -- Copy and resize part of an image with resampling
imagecopyresized -- Copy and resize part of an image
imagecreate -- Create a new palette based image
imagecreatefromgd2 -- Create a new image from GD2 file or URL
imagecreatefromgd2part -- Create a new image from a given part of GD2 file or URL
imagecreatefromgd -- Create a new image from GD file or URL
imagecreatefromgif -- Create a new image from file or URL
imagecreatefromjpeg -- Create a new image from file or URL
imagecreatefrompng -- Create a new image from file or URL
imagecreatefromstring -- Create a new image from the image stream in the string
imagecreatefromwbmp -- Create a new image from file or URL
imagecreatefromxbm -- Create a new image from file or URL
imagecreatefromxpm -- Create a new image from file or URL
imagecreatetruecolor -- Create a new true color image
imagedashedline -- Draw a dashed line
imagedestroy -- Destroy an image
imageellipse -- Draw an ellipse
imagefill -- Flood fill
imagefilledarc -- Draw a partial ellipse and fill it
imagefilledellipse -- Draw a filled ellipse
imagefilledpolygon -- Draw a filled polygon
imagefilledrectangle -- Draw a filled rectangle
imagefilltoborder -- Flood fill to specific color
imagefilter -- Applies a filter to an image
imagefontheight -- Get font height
imagefontwidth -- Get font width
imageftbbox -- Give the bounding box of a text using fonts via freetype2
imagefttext -- Write text to the image using fonts using FreeType 2
imagegammacorrect -- Apply a gamma correction to a GD image
imagegd2 -- Output GD2 image to browser or file
imagegd -- Output GD image to browser or file
imagegif -- Output image to browser or file
imagegrabscreen -- Captures the whole screen
imagegrabwindow -- Captures a window
imageinterlace -- Enable or disable interlace
imageistruecolor -- Finds whether an image is a truecolor image
imagejpeg -- Output image to browser or file
imagelayereffect -- Set the alpha blending flag to use the bundled libgd layering effects
imageline -- Draw a line
imageloadfont -- Load a new font
imagepalettecopy -- Copy the palette from one image to another
imagepng -- Output a PNG image to either the browser or a file
imagepolygon -- Draws a polygon
imagepsbbox -- Give the bounding box of a text rectangle using PostScript Type1 fonts
imagepsencodefont -- Change the character encoding vector of a font
imagepsextendfont -- Extend or condense a font
imagepsfreefont -- Free memory used by a PostScript Type 1 font
imagepsloadfont -- Load a PostScript Type 1 font from file
imagepsslantfont -- Slant a font
imagepstext -- Draws a text over an image using PostScript Type1 fonts
imagerectangle -- Draw a rectangle
imagerotate -- Rotate an image with a given angle
imagesavealpha -- Set the flag to save full alpha channel information (as opposed to single-color transparency) when saving PNG images
imagesetbrush -- Set the brush image for line drawing
imagesetpixel -- Set a single pixel
imagesetstyle -- Set the style for line drawing
imagesetthickness -- Set the thickness for line drawing
imagesettile -- Set the tile image for filling
imagestring -- Draw a string horizontally
imagestringup -- Draw a string vertically
imagesx -- Get image width
imagesy -- Get image height
imagetruecolortopalette -- Convert a true color image to a palette image
imagettfbbox -- Give the bounding box of a text using TrueType fonts
imagettftext -- Write text to the image using TrueType fonts
imagetypes -- Return the image types supported by this PHP build
imagewbmp -- Output image to browser or file
imagexbm -- Output XBM image to browser or file
iptcembed -- Embed binary IPTC data into a JPEG image
iptcparse -- Parse a binary IPTC block into single tags.
jpeg2wbmp -- Convert JPEG image file to WBMP image file
png2wbmp -- Convert PNG image file to WBMP image file