PHP Manual: Set the alpha blending flag to use layering effects

Description

true imagelayereffect(GdImage $image, int $effect)

Set the alpha blending flag to use layering effects.

Parameters

image

A GdImage object, returned by one of the image creation functions, such as imagecreatetruecolor.

effect

One of the following constants:

IMG_EFFECT_REPLACE: Use pixel replacement (equivalent of passing true to imagealphablending)
IMG_EFFECT_ALPHABLEND: Use normal pixel blending (equivalent of passing false to imagealphablending)
IMG_EFFECT_NORMAL: Same as IMG_EFFECT_ALPHABLEND.
IMG_EFFECT_OVERLAY: Overlay has the effect that black background pixels will remain black, white background pixels will remain white, but grey background pixels will take the colour of the foreground pixel.
IMG_EFFECT_MULTIPLY: Overlays with a multiply effect.

Return Values

Always returns true.

Changelog

Version	Description
8.0.0	`image` expects a GdImage instance now; previously, a valid `gd` resource was expected.
7.2.0	Added `IMG_EFFECT_MULTIPLY` (requires system libgd >= 2.1.1 or the bundled libgd).

Examples

Example #1 imagelayereffect example

<?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($im, 50, 50, 50, 80, imagecolorallocate($im, 100, 100, 255));
imagefilledellipse($im, 50, 50, 80, 50, imagecolorallocate($im, 255, 100, 100));

// Output
header('Content-type: image/png');

imagepng($im);
?>

The above example will output something similar to: