Returns the index of the color of the pixel at the
specified location in the image specified by
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:
An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
x-coordinate of the point
y-coordinate of the point