int imagecolorallocate(int im, int red, int green, int blue);
ImageColorAllocate returns a color identifier representing the color composed of the given RGB components. The im argument is the return from the imagecreate() function. ImageColorAllocate must be called to create each color that is to be used in the image represented by im.
$white = ImageColorAllocate($im, 255,255,255); $black = ImageColorAllocate($im, 0,0,0);