[gs-bugs] [Bug 691152] Gradient issues with tiffsep

bugzilla-daemon at ghostscript.com bugzilla-daemon at ghostscript.com
Wed Jun 1 17:10:14 UTC 2011


http://bugs.ghostscript.com/show_bug.cgi?id=691152

--- Comment #9 from Robin Watts <robin.watts at artifex.com> 2011-06-01 17:10:12 UTC ---
There are 2 components to this bug.

1) That tiffsep and tiff24nc give different results
2) That tiff24nc gives the wrong result.

1) is explained by the fact that tiffsep has "non separable and linear colors",
and tiff24nc has "separable and linear colours". This means that the shadings
end up decomposed into linearly filled traps in one, and constant color traps
in the other.

This wouldn't matter if the targets of the decomposition were small enough (1
pixel in size), but they aren't beecause of...

2) The commit that marcos points to (rev 7936, git hash 81fb15c), changes the
shading code to only decompose to 1 pixel, or one point, whichever is larger.
His claim was that we'd never notice differences in shadings smaller than this.

I don't believe that's true, especially as people frequently abuse the
resolution field to get images large enough to support zooming.

I am tempted to revert the change - but need to test the timing differences it
makes. Ken suggested a setting (perhaps -dSHADINGQUALITY=) along the lines of
jpeg quality.

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