Question

When should I go with core graphics over images for making a custom UIButton?
Is core graphics faster? Other than resolution independence, are there any other major benefits?

Answer 1

Pros of Core Graphics:

• Code for drawing a button will probably be smaller than an image file.
• Allows dynamic modification, slight changes without adding a complete second image.
• As you mentioned, resolution independent.
• Less memory intensive (doesn’t allocate memory to hold every pixel).

Pros of images:

• Creating the image in an editor will usually be simpler than writing code which draws it perfectly. (If you use anything other than solid colors, it could be much simpler.)
• The editor will let you see the image beforehand without recompiling.
• Easier to work with other built in objects (i.e., you can make it the background of a UIButton).

As for running time, I am not sure. I would guess that CG would be faster for simple drawing, where most of the pixels aren’t changed, but images would be faster for more complex drawing where most of the pixels are changed (Assuming you use the PNG format, so it gets optomized. Otherwise, CG would probably always be faster).

As a compromise, you could draw into an image once, and use that image for future drawing. This would allow you to get some of the benefits from each.