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PHP provides a wealth of image processing functions, mainly including:
| Function | Description |
|---|---|
| gd_info() | Get information about the installed GD library |
| getimagesize() | Get image information |
| getimagesizefromstring() | Get image information |
| image_type_to_extension() | Get the image suffix |
| image_type_to_mime_type() | Return the MIME type of the image |
| image2wbmp() | Output WBMP image |
| imageaffine() | Return the image after affine transformation |
| imageaffinematrixconcat() | Concatenate two matrices |
| imageaffinematrixget() | Obtain the matrix |
| imagealphablending() | Set the mixing mode of the image |
| imageantialias() | Whether to use the antialias (antialias) feature |
| imagearc() | Draw an elliptical arc |
| imagechar() | Write horizontal characters |
| imagecharup() | Draw a character vertically |
| imagecolorallocate() | Allocate color for an image |
| imagecolorallocatealpha() | Allocate color and opacity for an image |
| imagecolorat() | Get the color index value of a pixel |
| imagecolorclosest() | Get the index value of the closest color to the specified color |
| imagecolorclosestalpha() | Get the index of the closest color with transparency to the specified color |
| imagecolorclosesthwb() | Get the index of the closest grayscale shade to the specified color |
| imagesx() , imagesy() | Get image width and height |
To use PHP image processing functions, you need to load the GD support library. Please make sure that the GD library is loaded in php.ini:
On Windows servers:
extension = php_gd2.dll
On Linux and Mac systems:
extension = php_gd2.so
You can use the gd_info() function to view information about the currently installed GD library:
<?php var_dump(gd_info()); ?>
Output is roughly as follows:
array(12) {
["GD Version"]=>
string(26) "bundled (2.1.0 compatible"
["FreeType Support"]=>
bool(true)
["FreeType Linkage"]=>
string(13) "with freetype"
["T1Lib Support"]=>
bool(false)
["GIF Read Support"]=>
bool(true)
["GIF Create Support"]=>
bool(true)
["JPEG Support"]=>
bool(true)
["PNG Support"]=>
bool(true)
["WBMP Support"]=>
bool(true)
["XPM Support"]=>
bool(false)
["XBM Support"]=>
bool(true)
["JIS-mapped Japanese Font Support"]=>
bool(false)
}