A Boolean value indicating whether the image data has an alpha channel.
- macOS 10.0+
The value of this property is
YES if the receiver has a known alpha channel; otherwise,
Subclasses can set this property when loading image data to notify the parent class whether that data contains an alpha component. Specifying a value of
YES does not add an alpha channel to the image data itself; it merely records the fact that the data has an alpha channel.