Description
int 
imagecolorat ( resource image, int x, int y )
    Returns the index of the color of the pixel at the
    specified location in the image specified by image.
   
    If PHP is compiled against GD library 2.0 or higher and the image is a
    truecolor image, this function returns the RGB value of that pixel as
    integer. Use bitshifting and masking to access the distinct red, green and blue
    component values:
    
| Example 1. Access distinct RGB values | 
<?php$im = ImageCreateFromPng("rockym.png");
 $rgb = ImageColorAt($im, 100, 100);
 $r = ($rgb >> 16) & 0xFF;
 $g = ($rgb >> 8) & 0xFF;
 $b = $rgb & 0xFF;
 ?>
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    See also imagecolorset() and
    imagecolorsforindex().