This key specifies whether the image data in a grayscale image should be treated as alpha information. The value for this key is an
NSNumber object that specifies a boolean value. If
NO, the image data is treated as luminance data. If
YES, the image data is treated as alpha data. The default value is
NO. This key is ignored if the source image is not a grayscale image.
- iOS 5.0+
- macOS 10.14+
- tvOS 9.0+