<?php
/**
 * Colorize an image with a given color. 
 *
 * It is directly modifying the image given as input (side effect).
 *
 * Based on a function given by Davide Candiloro:
 *  http://www.php.net/manual/en/function.imagecolorset.php
 *
 * Example of use:
 *
 *   $im = imagecreatefrompng('someimage.png');
 *   colorize($im, array('red'=>249, 'green'=>232, 'blue'=>89));
 *   imagepng($im, 'output.png');
 *   imagedestroy($im);
 *
 * @param resource Image created with for example imagecreatefrompng.
 * @param array Associative array with 'red', 'green' and 'blue' values
 * @return resource The input resource image colorized.
 *
 */
function colorize($im, $color)
{
    imagetruecolortopalette($im, FALSE, 256);
    $ncolors = imagecolorstotal($im);
    for ($c = 0; $c<$ncolors; $c++) { 
        $col = imagecolorsforindex($im, $c);          
        // replaces original greyscale palette with a colorized one.
        imagecolorset($im, $c, $color['red']*$col['red']/256, 
                               $color['green']*$col['green']/256, 
                               $color['blue']*$col['blue']/256); 
    }
    return $im;
}

?>