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Fix example in QOI_OP_LUMA documentation; close #161

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Dominic Szablewski 2022-01-05 16:51:38 +01:00
parent a27f8ed459
commit 6804a745e4
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qoi.h
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@ -173,8 +173,8 @@ The alpha value remains unchanged from the previous pixel.
The green channel is used to indicate the general direction of change and is
encoded in 6 bits. The red and blue channels (dr and db) base their diffs off
of the green channel difference and are encoded in 4 bits. I.e.:
dr_dg = (last_px.r - cur_px.r) - (last_px.g - cur_px.g)
db_dg = (last_px.b - cur_px.b) - (last_px.g - cur_px.g)
dr_dg = (cur_px.r - prev_px.r) - (cur_px.g - prev_px.g)
db_dg = (cur_px.b - prev_px.b) - (cur_px.g - prev_px.g)
The difference to the current channel values are using a wraparound operation,
so "10 - 13" will result in 253, while "250 + 7" will result in 1.