(PHP 4 >= 4.3.2, PHP 5)
imageistruecolor() finds whether the image
image is a truecolor image.
An image resource, returned by one of the image creation functions,
such as imagecreatetruecolor().
Returns TRUE if the image is truecolor, FALSE
Note: This function requires GD 2.0.1 or later (2.0.28 or later is recommended).