Whether to retain full alpha channel information when saving images

# imagesavealpha

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

imagesavealpha — Whether to retain full alpha channel information when saving images

### Description

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

imagesavealpha() sets the flag which determines whether to retain full alpha channel information (as opposed to single-color transparency) when saving images. This is only supported for image formats which support full alpha channel information, i.e. `PNG`, `WebP` and `AVIF`.

> Note: imagesavealpha() is only meaningful for `PNG` images, since the full alpha channel is always saved for `WebP` and `AVIF`. It is not recommended to rely on this behavior, as it may change in the future. Thus, imagesavealpha() should be called deliberately also for `WebP` and `AVIF` 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

Always returns `true`.

### Changelog

Version | Description
--- | ---
8.0.0 | `image` expects a GdImage instance now; previously, a valid `gd` resource was expected.

### Examples

Example #1 Basic imagesavealpha() Usage

`<?php
// Load a png image with alpha channel
$png = imagecreatefrompng('./alphachannel_example.png');
// Turn off alpha blending
imagealphablending($png, false);
// Do desired operations
// Set alpha flag
imagesavealpha($png, true);
// Output image to browser
header('Content-Type: image/png');
imagepng($png);
?>`

### See Also

- imagealphablending() - Set the blending mode for an image

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