ImageCreate v. ImageCreateTrueColor

Hello, I'm making an Image and I was wondering what the difference is between these two Image constructors. I need to find a way to make dotted and dashed lines (according to different patterns I've been given) and I want the sections between the dots to be transparent. I'm planning on using the ImageSetStyle function. From what I read on PHP.net, some things cannot be used with ImageCreateTrueColor, but it looks like some can only be used that one. One thing I'm interested in is the constant IMG_COLOR_TRANSPARENT - can this be used with ImageCreate? Is there a reason I should use one of the constructors over the other? Thanks! -Natalie Natalie S. Leotta Information Management Services, Inc. (301) 680-9770 LeottaN@ims.nci.nih.gov