Created attachment 1574 [details] ps file drawing manually some filled rectangles
On gnuplot-beta@lists.sourceforge.net, there is a discussion about ghostscript's bug which influences plots (maps) with adjacent filled rectangles and antialiasing with "-dGraphicsAlphaBits=4". See the mailing group archive of July 2005 http://sourceforge.net/mailarchive/forum.php?thread_id=7783155&forum_id=6027 and messages entitled spurious lines in gs with antialiasing /f + /h, color box To reproduce the bug: draw the enclosed attachment in ghostview, and set "antialiasing" on. If you don't see spurious white/yellowish lines in between gray rectangles, then change the resolution/scale. Another way to reproduce it easily is to raster the ps file to png, by a script like this: a=demo3.ps #A="-dTextAlphaBits=4 -dGraphicsAlphaBits=4" #A="-dTextAlphaBits=4" A="-dGraphicsAlphaBits=4" # Choose either of two: D=png16m #D=png256 gs8 -q -r20 $A -sDEVICE=$D \ -dSAFER -dNOPAUSE -dBATCH -sOutputFile=$a.png $a -quit #ps2pdf $A $a $a.pdf You can play with the definition of "/F" in the demo file. When using /F {closepath gsave stroke grestore fill} def then it is less visible than without stroke. The bug has been confirmed on gs 7.07.x, 8.50. It is not present in Adobe Distiller. In gnuplot 4.0, you create a ps file showing the error by commands: set pm3d map set samples 200,200 set isosamples 100,100 splot x set term post color; set out 'a.ps' replot set term pop; set out See the map or the colorbox on the right. Could ghostscript fix this bug? How can we change the ps code produced by gnuplot so that the bug it not apparent even for current gs versions? Is there something like "gs should not antialias this section"? Users complain that the colorbox looks ugly when they have antialiasing switched on.
Created attachment 1578 [details] foo.ps -- modified sample This is an old and rather difficult to fix issue. See the bug 687742 for the discussion. gnuplot can try to write adjacent boxes in the single fill operation but this is not possible when the bxes have different colors. See the modified sample file.
We need to draw a colour map, i.e. all rectangles/quadrangles have different colour. Isn't there any other possibility how to change gs's GraphicsAlphaBits from within the postscript code, or to disable the antialiasing within a given part of the ps file?
I can't remember what the resolution of this bug was supposed to be, but the issue is being discussed again in Bug 689557. Closing this one in favor of the newer one. *** This bug has been marked as a duplicate of 689557 ***