[libpng18] [bug fix] Adjust colorspace calculations for ACES AP0 #609
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The subtracts in PNG_XYZ_from_xy are producing integer overflow with some valid but extreme xy values. This re-introduces the previous checks, but with less limited bounds; sufficient to accomodate the ACEScg end points (ACES AP1), but not for the ACES AP0 end points. Those were not working anyway because libpng reads the cHRM parameters as unsigned values, so they must always be at least 0. A better solution requires recognizing reasonable negative values (ones which violate the current spec) and allowing them too, at least on read. Reviewed-by: Cosmin Truta <[email protected]> Signed-off-by: John Bowler <[email protected]> Signed-off-by: Cosmin Truta <[email protected]>
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Since I've dropped trying to fix the math problems in general there is no merit to fixing them here so this change should now go in to libpng18. |
jbowler
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The subtracts in PNG_XYZ_from_xy are producing integer overflow with
some valid but extreme xy values. This re-introduces the previous
checks, but with less limited bounds; sufficient to accomodate the
ACEScg end points (ACES AP1), but not for the ACES AP0 end points.
Those were not working anyway because libpng reads the cHRM parameters
as unsigned values, so they must always be at least 0.
A better solution requires recognizing reasonable negative values (ones
which violate the current spec) and allowing them too, at least on read.
Reviewed-by: Cosmin Truta [email protected]
Signed-off-by: John Bowler [email protected]
Signed-off-by: Cosmin Truta [email protected]