How do I create an 8-bit PNG with transparency from an NSBitmapImageRep?
- by Rob Keniger
I have a 32-bit NSBitmapImageRep which has an alpha channel with essentially 1-bit values (the pixels are either on or off).
I want to save this bitmap to an 8-bit PNG file with transparency. If I use the -representationUsingType:properties: method of NSBitmapImageRep and pass in NSPNGFileType, a 32-bit PNG is created, which is not what I want.
I…