_cogl_bitmap_fallback_convert now supports converting to and from all
of the pixel formats, except it continues to preserve the premult
status of the original bitmap. The pixels are unpacked into a
temporary buffer that is either 8-bits per component or 16-bits per
component RGBA depending on whether the destination format is going to
use more than 8 bits per component (eg RGBA_1010102). The packing and
unpacking code is stored in a separate header which is included twice
to generate the functions needed for both sizes of unpacked data. The
hope is that when converting between two formats that are both 8-bit
sized, such as swizzling between BGRA and RGBA, then the
multiplications and divisions in the code will be optimized out and it
shouldn't be too inefficient. Previously the inner switch statement to
decide which conversion to use only operated on one pixel at a time so
it was probably relatively slow.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
