I'm working on a package which includes rescaling of images in PHP. For image rescaling, PHP has the GD and ImageMagick libraries. Are those likely to be part of a given client's PHP install already?
Is there a "default" install of PHP, for that matter? By default, are either GD or ImageMagick included?
If neither is installed, should I have some sort of horrible fallback position of reading, rescaling, and saving GIFs, JPGs, and PNGs, or is it simple to add GD or ImageMagick to an existing install?