Change the number of bits per color component.
The bit depths you should use are 1, 2, 4, 8 or 16. Other values
are not supported in the PDF Specification.
Changing this property for Indexed color images changes the
precision of the index rather than of the color components. If you
want to change the precision of the components you need to Realize the PixMap first.
Operations like Resize operate more
naturally on eight and sixteen bit images - producing better
results, faster, using less memory. So if you will be resizing and
also moving to eight or sixteen bit depth it is typically better to
Resample before calling Resize.
After this method is called the image may no longer be longer
compressed. You may wish to compress it using the StreamObject.Compress