Convert some graphics to 2 bpp Grayscale

[Narishma-gb]

Some of the gifs in gfx/ use RGB or GRAY 8 bpp encoding, some also with alpha. This changes them all to 2 bpp GRAY.
Most of the files deflate in size except gfx/pikachu/unknown_e40cc.png, which was previously 8 bpp gray, and probably used a better compression algorithm. I used ImageMagick to output the files.

[Rangi42]

% find gfx -name '*.png' -exec file {} \+ | \grep -v ', [12]-bit grayscale, non-interlaced' | sort 
gfx/diploma/diploma.png:                    PNG image data, 128 x 64, 8-bit/color RGBA, non-interlaced
gfx/intro/clouds.png:                       PNG image data, 16 x 32, 8-bit/color RGBA, non-interlaced
gfx/pikachu/unknown_e40cc.png:              PNG image data, 40 x 8, 8-bit grayscale, non-interlaced
gfx/pikachu/unknown_e41d2.png:              PNG image data, 40 x 16, 8-bit grayscale, non-interlaced
gfx/pikachu/unknown_e444b.png:              PNG image data, 40 x 32, 8-bit grayscale, non-interlaced
gfx/pikachu/unknown_e4a99.png:              PNG image data, 40 x 16, 8-bit grayscale, non-interlaced
gfx/pokemon/front/electrode.png:            PNG image data, 40 x 40, 8-bit/color RGB, non-interlaced
gfx/sprites/bulbasaur.png:                  PNG image data, 16 x 48, 8-bit/color RGBA, non-interlaced
gfx/sprites/chansey.png:                    PNG image data, 16 x 48, 8-bit/color RGBA, non-interlaced
gfx/sprites/clefairy.png:                   PNG image data, 16 x 48, 8-bit/color RGBA, non-interlaced
gfx/sprites/james.png:                      PNG image data, 16 x 96, 8-bit/color RGBA, non-interlaced
gfx/sprites/jessie.png:                     PNG image data, 16 x 96, 8-bit/color RGBA, non-interlaced
gfx/sprites/jigglypuff.png:                 PNG image data, 16 x 48, 8-bit/color RGBA, non-interlaced
gfx/sprites/oddish.png:                     PNG image data, 16 x 48, 8-bit/color RGBA, non-interlaced
gfx/sprites/officer_jenny.png:              PNG image data, 16 x 96, 8-bit/color RGBA, non-interlaced
gfx/sprites/pikachu.png:                    PNG image data, 16 x 96, 8-bit/color RGBA, non-interlaced
gfx/sprites/question_mark.png:              PNG image data, 16 x 16, 8-bit/color RGBA, non-interlaced
gfx/sprites/sandshrew.png:                  PNG image data, 16 x 48, 8-bit/color RGBA, non-interlaced
gfx/sprites/surfing_pikachu.png:            PNG image data, 16 x 96, 8-bit/color RGBA, non-interlaced
gfx/title/pokemon_logo_japan.png:           PNG image data, 128 x 48, 8-bit/color RGBA, non-interlaced

Nice catch! Note that https://github.com/pret/gb-asm-tools has palfix.py which can also help with this sort of thing.

[Narishma-gb]

Wow, I didn't know you could grep that sort of things! I had to use a small c script to sort and peek inside the png headers. Thanks!