A way to read the color of a pixel

method:imagecolorat($img, $x, $y)

example
<?php
$img = imagecreatefrompng("image1.png");

$w = imagesx($img);
$h = imagesy($img);

for($y=0;$y<$h;$y++) { for($x=0;$x<$w;$x++) { $rgb = imagecolorat($img, $x, $y); $r = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b = $rgb & 0xFF;
echo "#".str_repeat("0",2-strlen(dechex($r))).dechex($r).
str_repeat("0",2-strlen(dechex($g))).dechex($g).
str_repeat("0",2-strlen(dechex($b))).dechex($b).",";
}
echo "
\r\n";
}
>

Reference
http://php.net/manual/en/book.image.php