The blit loops are all converting each pixel to the destination format
rather than creating a converted color table and just using a lookup
to convert the image.
Also, if the IndexColorModel contains all gray values, then the image is
tagged as "Index8Gray" internally and there are no blit loops for images
of these formats to the popular screen formats. These images can use the
same loops as the indexed color images, so the same loops should be
registered for both types of formats.