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PNGOUT: scanline length and block split threshold relation (/b option)
- Please correct me if I'm wrong.
If I'd like to try deflate blocks that contain exactly n scanlines of an image I should set the /b option this way:
n x (1 + line length) : 256 colors paletted or 8 bits greyscale (type 3 and 0)
n x (1 + 2 x line length) : 8 bits grey with alpha (type 4)
n x (1 + 3 x line length) : 24 bits RGB (type 2)
n x (1 + 4 x line length) : 32 bits RGB with alpha (type 6)
The extra one is the PNG filter type byte. Re: PNGOUT: scanline length and block split threshold relation (/b option)
The /b option does not work like that. It is a threshold that tells PNGOUT when it is worthwhile to split a block. Neither /b or /n give you any control over what byte offset in the image the splitting actually occurs.