is it possible to remove a black background from an image to make it transparent using GD
can i pass the radius of the moon to GD (as it is on the image) and have it slice the moon out so to speak leaving it on a transparent background?
GD question (cut out background make transparent)
To do that, you'd have to also know where the center of the moon is.
Instead, why not just create a true color image and use [man]imagecolortransparent/man to indicate the transparent color.
only issue being, say the moon is in half phase... while there may be a faint outline on the darkened area, if there is true black in other areas, it too will be transparent