[Feature request] Support non-tiled "streams" of PNG-to-1bpp/2bpp conversion

[Rangi42]

If an input image is 8px wide, and the only output is graphics data (no tilemap, attrmap, palmap, or palette), and there's no deduplication or mirroring, then it's not necessary to divide the image into tiles: RGBGFX can just process the graphic one pixel row at a time.

This would occasionally be useful, e.g. for this sprite in pokered:

MinimizedMonSprite:
; 8x5 partial tile graphic
pusho b.X ; . = 0, X = 1
	db %...XX...
	db %..XXXX..
	db %.XXXXXX.
	db %..XXXX..
	db %..X..X..
popo
MinimizedMonSpriteEnd:

It's been requested before in #234 (comment) (as noted in #981 (comment)), and semi-supported by 8fe5293.

[Rangi42]

This could combine with #1005, depending on how that behaves. You could declare the entire image to be one "dedup unit" large.

[Rangi42]

Arguably/alternatively, "stream" mode wouldn't have to be limited to 8px wide images; it could just process any input image in column-major order (as if given -Z). It would still need width to be a multiple of 8px. I imagine that some long streamed input would be nicer to work with if it didn't have to be a really tall vertical image.