Applies an image effect such as grayscale, brightness or contrast.
What It Does
GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. Available filters and argument ranges depend on the filter type.
Requirements and Compatibility
GD extension. Sample images and fonts referred to by filename must be supplied locally. Use PHP 8 GdImage objects where applicable; optional decoders depend on the installed build.
Syntax, Inputs and Results
The arguments shown below are concrete values for this function; their types and ranges matter. The example checks return data rather than assuming that every operation succeeds.
Example 1: Basic Use
Call the function with a concrete input and inspect its result.
<?php
if (!extension_loaded('gd')) throw new RuntimeException('GD extension required');
$im = imagecreatetruecolor(160, 110);
$white = imagecolorallocate($im, 255, 255, 255);
imagefilledrectangle($im, 0, 0, 159, 109, $white);
$blue = imagecolorallocate($im, 34, 92, 166);
imagefilledrectangle($im, 8, 8, 120, 72, $blue);
$ok = imagefilter($im, IMG_FILTER_GRAYSCALE);
var_dump($ok);Example 2: Another Case
Change the inputs to observe the behavior on another case.
<?php
if (!extension_loaded('gd')) throw new RuntimeException('GD extension required');
$im = imagecreatetruecolor(160, 110);
$white = imagecolorallocate($im, 255, 255, 255);
imagefilledrectangle($im, 0, 0, 159, 109, $white);
$blue = imagecolorallocate($im, 34, 92, 166);
imagefilledrectangle($im, 8, 8, 120, 72, $blue);
$ok = imagefilter($im, IMG_FILTER_BRIGHTNESS, 25);
var_dump($ok);Practical Example
Use the result to create an output, validate a condition, or complete an image workflow.
<?php
if (!extension_loaded('gd')) throw new RuntimeException('GD extension required');
$im = imagecreatetruecolor(160, 110);
$white = imagecolorallocate($im, 255, 255, 255);
imagefilledrectangle($im, 0, 0, 159, 109, $white);
imagefilter($im, IMG_FILTER_BRIGHTNESS, 25);
if (!imagepng($im, __DIR__ . "/imagefilter-demo.png")) throw new RuntimeException("Unable to save");For production, apply the compatibility and edge-case limits described below.
Important Behavior and Edge Cases
Available filters and argument ranges depend on the filter type.
Comparison with Related Functions and Tools
| Subject | Key difference |
|---|---|
| imagefilter() | GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Calling imagefilter() without its required input or supported extension | Check the extension, supply valid arguments, and handle false or exceptions according to the function. |
| Assuming imagefilter() guarantees a valid or safe image | Available filters and argument ranges depend on the filter type. |
| Confusing the operation with a related API | GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. |
Key Takeaways
- Applies an image effect such as grayscale, brightness or contrast.
- Available filters and argument ranges depend on the filter type.
- Choose the companion API described in the comparison table when the job differs.
Use these examples as a starting point, then validate the result with the actual PHP build, dependencies and inputs used by your application.