Returns a newly scaled GdImage with selected dimensions and interpolation.
What It Does
GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. An aspect-ratio dimension of -1 is computed automatically; check return for failure.
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);
$image = imagescale($im, 80, 60, IMG_BILINEAR_FIXED);
if (!$image instanceof GdImage) throw new RuntimeException('Image transformation failed');
echo imagesx($image), ' x ', imagesy($image);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);
$image = imagescale($im, 50, -1, IMG_NEAREST_NEIGHBOUR);
if (!$image instanceof GdImage) throw new RuntimeException('Image transformation failed');
echo imagesx($image), ' x ', imagesy($image);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);
$image = imagescale($im, 50, -1, IMG_NEAREST_NEIGHBOUR);
if (!$image instanceof GdImage) throw new RuntimeException('Image transformation failed');
echo imagesx($image), ' x ', imagesy($image);
imagepng($image, __DIR__ . "/transformed-imagescale.png");For production, apply the compatibility and edge-case limits described below.
Important Behavior and Edge Cases
An aspect-ratio dimension of -1 is computed automatically; check return for failure.
Comparison with Related Functions and Tools
| Subject | Key difference |
|---|---|
| imagescale() | GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. |
Common Beginner Mistakes
| Mistake | Correct approach |
|---|---|
| Calling imagescale() without its required input or supported extension | Check the extension, supply valid arguments, and handle false or exceptions according to the function. |
| Assuming imagescale() guarantees a valid or safe image | An aspect-ratio dimension of -1 is computed automatically; check return for failure. |
| Confusing the operation with a related API | GD provides simple pixel-level operations; Imagick provides another image-processing API with distinct requirements. |
Key Takeaways
- Returns a newly scaled GdImage with selected dimensions and interpolation.
- An aspect-ratio dimension of -1 is computed automatically; check return for failure.
- 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.