build a table that decodes both magnitude and value of small ACs in one go.

decode image to YCbCr format

this function is designed to support animated gifs, although stb_image doesn't support it

@OPTIMIZE: store non-zigzagged during the decode passes, and only de-zigzag when dequantizing

after we see SOS

returns number of contours

rects array must be big enough to accommodate all characters in the given ranges

rects array must be big enough to accommodate all characters in the given ranges

note: this routine clips fills that extend off the edges... ideally this wouldn't happen, but it could happen if the truetype glyph bounding boxes are

tesselate until threshhold p is happy... @TODO warped to compensate for non-linear stretching