Original calculation (bits += (ri_stride - ri_emustride) / 2) was
incorrect because stride may be wider than visible width.
Fix in 1.33 (bits += (ri_width - ri_emustride) / 2) was incorrect
because units do not match; "bits" and "ri_emustride" are in bytes,
but "width" is in pels. Works by accident for 8bpp displays.
Change to bits += ((ri_width * bpp / 8) - ri_emustride) / 2
to correctly account for visible width and bpp.
54caa65cf6