PHP Manual: imagecolorstotal

function imagecolorstotal(GdImage $image): int

Returns the number of colors in an image palette.

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

Returns the number of colors in the specified image's palette or 0 for truecolor images.

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

Example #1 Getting total number of colors in an image using imagecolorstotal()

<?php
// Create image instance
$im = imagecreatefromgif('php.gif');

echo 'Total colors in image: ' . imagecolorstotal($im);
?>

The above example will output something similar to:

Total colors in image: 128

imagecolorstotal