Index for the resolution of the displayed image.
The index can range from 0 through (NumberOfResolutions -1). A resolution index equal to zero represents the highest resolution and the NumberOfResolutions represents the lowest resolution. So if the NumberOfResolutions equals 3 and the image size is 200x100, then this function will return 200x100 when the resolution index equals zero, 100x50 when the resolution index equals 1, and 50x25 when the resolution index equals 2.
For an example that displays the resolution index after ZoomIn has been called, refer to JpipRasterImageViewer.