imagesavealpha

(PHP 4 >= 4.3.2, PHP 5, PHP 7, PHP 8)

imagesavealphaWhether to retain full alpha channel information when saving PNG images

Description

imagesavealpha(GdImage $image, bool $enable): bool

imagesavealpha() sets the flag which determines whether to retain full alpha channel information (as opposed to single-color transparency) when saving PNG images.

Alphablending has to be disabled (imagealphablending($im, false)) to retain the alpha-channel in the first place.

Parameters

image

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

enable

Whether to save the alpha channel or not. Defaults to false.

Return Values

Returns true on success or false on failure.

Changelog

Version Description
8.0.0 image expects a GdImage instance now; previously, a resource was expected.

Examples

Example #1 Basic imagesavealpha() Usage

<?php
// Load a png image with alpha channel
$png imagecreatefrompng('./alphachannel_example.png');

// Turn off alpha blending
imagealphablending($pngfalse);

// Do desired operations

// Set alpha flag
imagesavealpha($pngtrue);

// Output image to browser
header('Content-Type: image/png');

imagepng($png);
imagedestroy($png);
?>

See Also