How do I create an alpha only bitmap context

Question

Apple tech note QA1037 says \"To create an alpha-only bitmap context simply pass NULL for the colorspace parameter.\"

However, I am not sure what to pass for the

Answer 1

The docs clearly state you can use values from the CGImageAlphaInfo even though the parameter is defined as needed a value from the CGBitmapInfo enum.

One solution would be to cast the value:

(CGBitmapInfo)kCGImageAlphaOnly

That will make the compiler happy.