Latest work on the bmp on-load scaler:

Macros for calculating size needed for bitmap load and scaling, so that
these can be compile-time constant when their inputs are.

Reduce size of bayer dither by chopping all but first row of dither
matrix, and replacing 2D lookup with 1D lookup and small calculation.

Move some functions not related to actual bmp file loading out of bmp.c.

A smaller brightness() for mono targets, and a higher-quality one for
greyscale targets, both replacing the division by 10 with a shift.

Port of the linear and area scalers to greyscale targets, this costs
some binsize but produces better output even when dithered to 2bpp.

Move duplicated row output code from inside vertical scalers to a
separate row output function.

Move some multiplies out of the line scaler, for a small speedup and
code size reduction, as well as a small improvement in accuracy for the
upscaling case.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19592 a1c6a512-1295-4272-9138-f99709370657
8 files changed