imagesavealpha

Whether to retain full alpha channel information when saving images

&reftitle.description; `bool` `imagesavealpha` `GdImage` `image` `bool` `enable`

`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`.

`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.

&reftitle.parameters;

&gd.image.description;

`enable`

- Whether to save the alpha channel or not. Defaults to &false;.

&reftitle.returnvalues;

&return.success;

&reftitle.changelog;

&Version; | &Description;
&gd.changelog.image-param;

&reftitle.examples;

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

&reftitle.seealso;

- `imagealphablending`