<?php
header("Content-type: image/png");
$c = $_GET['color'];
if(!isset($_GET['color'])) $c = "#COR PADRAO AQUI";
function HexParaRGB($hex) {
        $hex = ereg_replace("#", "", $hex);
        $cor = array();

        if(strlen($hex) == 3) {
                $cor['r'] = hexdec(substr($hex, 0, 1) . $r);
                $cor['g'] = hexdec(substr($hex, 1, 1) . $g);
                $cor['b'] = hexdec(substr($hex, 2, 1) . $B);

        }elseif(strlen($hex) == 6) {
                $cor['r'] = hexdec(substr($hex, 0, 2));
                $cor['g'] = hexdec(substr($hex, 2, 2));
                $cor['b'] = hexdec(substr($hex, 4, 2));
        }
        return $cor;
}

$im = imagecreatefrompng("puffle.png");
$x = 0;
$y = 0;
$lar = imagesx($im);
$alt = imagesy($im);

for ($x=0;$x<=$lar;$x++){
  for ($y=0;$y<=$alt;$y++){
    $rgb = imagecolorat($im, $x, $y);
    $r = ($rgb >> 16) & 0xFF;
    $g = ($rgb >> 8) & 0xFF;
    $b = $rgb & 0xFF;
    $cor = $r.'-'.$g.'-'.$b;

    if($cor == '0-0-255'){
      $corHex = HexParaRGB($c);
      $color = imagecolorallocate($im, $corHex['r'], $corHex['g'], $corHex['b']);
      imagesetpixel($im, $x, $y, $color);
    }
  }
}

imagepng($im);
imagedestroy($im);
?>