(PHP 5 >= 5.5.0, PHP 7, PHP 8)
imagepalettetotruecolor — Converts a palette based image to true color
Converts a palette based image, created by functions like imagecreate() to a true color image, like imagecreatetruecolor().
imageA GdImage object, returned by one of the image creation functions, such as imagecreatetruecolor().
   Returns true if the convertion was complete, or if the source image already 
   is a true color image, otherwise false is returned.
  
| Version | Description | 
|---|---|
| 8.0.0 | imageexpects a GdImage
  instance now; previously, a validgdresource was expected. | 
Example #1 Converts any image object to true color
<?php
// Backwards compatiblity
if(!function_exists('imagepalettetotruecolor'))
{
    function imagepalettetotruecolor(&$src)
    {
        if(imageistruecolor($src))
        {
            return(true);
        }
        $dst = imagecreatetruecolor(imagesx($src), imagesy($src));
        imagecopy($dst, $src, 0, 0, 0, 0, imagesx($src), imagesy($src));
        imagedestroy($src);
        $src = $dst;
        return(true);
    }
}
// Helper closure
$typeof = function() use($im)
{
    echo 'typeof($im) = ' . (imageistruecolor($im) ? 'true color' : 'palette'), PHP_EOL;
};
// Create a palette based image
$im = imagecreate(100, 100);
$typeof();
// Convert it to true color
imagepalettetotruecolor($im);
$typeof();
// Free the memory
imagedestroy($im);
?>The above example will output:
typeof($im) = palette typeof($im) = true color