(PHP 4 >= 4.3.2, PHP 5)
imagesavealpha — Set the flag to save full alpha channel information (as opposed to single-color transparency) when saving PNG images
imagesavealpha() sets the flag to attempt to save full alpha channel information (as opposed to single-color transparency) when saving PNG images.
You have to unset alphablending (imagealphablending($im, false)), to use it.
Alpha channel is not supported by all browsers, if you have problem with your browser, try to load your script with an alpha channel compliant browser, e.g. latest Mozilla.
An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
Whether to save the alpha channel or not. Default to FALSE.
Returns TRUE on success or FALSE on failure.
Example #1 imagesavealpha() example
// Load a png image with alpha channels
$png = imagecreatefrompng('./alphachannel_example.png');
// Do required operations
// Turn off alpha blending and set alpha flag
// Output image to browser
Note: This function requires GD 2.0.1 or later (2.0.28 or later is recommended).