Master PHP Image Processing: Crop, Resize, Rotate & Watermark with Code Samples

PHP provides a set of image processing functions that enable developers to edit pictures directly on the server. Common tasks such as cropping, resizing, rotating, and adding watermarks can be performed with functions like imagecrop(), imagecopyresized(), imagecopyresampled(), imagerotate(), and imagestring().

Cropping an Image

Use imagecrop() to cut a rectangular region from a source JPEG. First load the image with imagecreatefromjpeg(), then specify the crop coordinates and dimensions.

$sourceImage = imagecreatefromjpeg('source.jpg');
$croppedImage = imagecrop($sourceImage, ['x' => 50, 'y' => 50, 'width' => 200, 'height' => 200]);
imagejpeg($croppedImage, 'cropped.jpg');
imagedestroy($sourceImage);
imagedestroy($croppedImage);

Resizing an Image

Both imagecopyresized() and imagecopyresampled() can scale an image. The example below halves the original dimensions using imagecopyresized().

$sourceImage = imagecreatefromjpeg('source.jpg');
$width = imagesx($sourceImage);
$height = imagesy($sourceImage);
$newWidth = $width * 0.5; // half size
$newHeight = $height * 0.5;
$targetImage = imagecreatetruecolor($newWidth, $newHeight);
imagecopyresized($targetImage, $sourceImage, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height);
imagejpeg($targetImage, 'resized.jpg');
imagedestroy($sourceImage);
imagedestroy($targetImage);

Rotating and Adding Watermarks

To rotate an image, call imagerotate(). Adding a text watermark can be done with imagestring(). Note that rotation may introduce distortion, so it should be used judiciously.

Best Practices

Always release image resources with imagedestroy() to avoid memory leaks. Proper error handling and checking return values are essential for stable and performant image manipulation.