Use ImageColorAt to map out pixel locations.

This is completely untested, but it should produce a (very large, depending on image size) two dimensional array with each pixel's colour value, so pixel x-56, y-22 will have a colour of $rgbValues[56][22].
<?php
$img = ImageCreateFromPng("<YOURIMAGE>.png");
$imgWidth = imagesx($img);
$imgHeight = imagesy($img);

for($x=1 ; $x<=$imgWidth ; $x++) {
  for($y=1 ; $y<=$imgHeight ; $y++) {
    $rgbValues[$x][$y] = ImageColorAt($img, $x, $y);
  }
}
?>

Hope this helps!

didn't work :(. It should output it in x and y.

Building on NickVd's code, just add another loop to print it.

for($x=1 ; $x<=$imgWidth ; $x++) {
  for($y=1 ; $y<=$imgHeight ; $y++) {
    echo "X=$x  Y=$y  Color=" . ImageColorAt($img, $x, $y);
  }
}

didn't work/

"After separating all the characters, it time to get the individual pixel point (x, y) of each pixel (1px width x height) in a character and store them for later comparison. The function we will be using is the "ImageColorAt", which basically gets the index of the color of a pixel. Using a loop to go through every single pixel, you would be able to filter out the white pixels apart from the pixels that forms the character (Table 1.0). Do this for the rest of the different characters and you should have a completed pixel index library for this kind of  image. (Table 2.0) show the complete pixel index librar.."