Use ImageColorAt to map out pixel locations.

Posted on 2007-04-01
Last Modified: 2009-12-16
I need to know how to use ImageColorAt to map out pixels in a png image. Then echo the results like this,

Point 1 : X - 1, Y - 19
Point 2 : X - 4, Y - 36
Point 3 : X - 6, Y - 11

It will be a loop, I know that much. Thanks
Question by:JPERKS1985
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Expert Comment

ID: 18831427
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].
$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!

Author Comment

ID: 18831460
didn't work :(. It should output it in x and y.
LVL 27

Expert Comment

ID: 18831510
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);
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Accepted Solution

NickVd earned 500 total points
ID: 18831936
No no no... There isn't a need for two different loops... just echo the value in the main loop..

for($x=1 ; $x<=$imgWidth ; $x++) {
  for($y=1 ; $y<=$imgHeight ; $y++) {
    $rgb = ImageColorAt($img, $x, $y);
    $rgbValues[$x][$y] = $rgb; // for later use...
    echo "X=$x  Y=$y  Color=" . $rgb;

Author Comment

ID: 18832917
didn't work/

Author Comment

ID: 18832919
"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.."

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