PHP imagelayereffect Function: Setting Alpha Blending for GD Layered Effects

The imagelayereffect function in PHP's GD library enables the setting of an alpha blending flag to apply layered effects such as overlay on an image resource.

Parameters : $image – a GD image resource created by functions like imagecreatetruecolor(); $effect – an integer constant specifying the effect (e.g., IMG_EFFECT_OVERLAY).

Return value : on success it returns the image resource; on failure it returns FALSE.

Example usage demonstrates creating a 100×100 image, filling a background, applying the overlay effect, drawing grey ellipses, sending the PNG header, outputting the image with imagepng, and freeing resources with imagedestroy:

<?php
// Setup an image
$im = imagecreatetruecolor(100,100);
// Set a background
imagefilledrectangle($im,0,0,100,100,imagecolorallocate($im,220,220,220));
// Apply the overlay alpha blending flag
imagelayereffect($im,IMG_EFFECT_OVERLAY);
// Draw two grey ellipses
imagefilledellipse($im,50,50,40,40,imagecolorallocate($im,100,255,100));
imagefilledellipse($im,50,50,80,80,imagecolorallocate($im,100,255,100));
imagefilledellipse($im,50,50,80,80,imagecolorallocate($im,255,100,100));
// Output
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
?>