Tells the delegate that the image object is about to access its underlying bitmap data.
- macOS 10.2+
The image object whose contents need to be loaded.
The image representation object that was accessed.
For incremental loading, this method is called when you first attempt to draw the image or otherwise access the bitmap data. Downloading of the image begins immediately after this method returns. This method is optional; incremental loading will continue if the delegate does not implement it.