Created attachment 7209 [details] fts_15_1515.png The stitch lines show up in the Ghostscript output at any resolution I've tried. The attachment shows the defect areas on the page generated using: gswin32c -r200 -sDEVICE=png16m -o fts_15_1515.png fts_15_1515.pdf I've cropped the image and circled the defects in red.
Created attachment 7212 [details] 1515_simplified.pdf A PDF file that just draws a small rectangular area showing that the lines all radiate in 8 directions from a single point in the shading. This is a ShadingType 4: 'Free form Gouraud-shaded triangle mesh'
Back to Ray from IRC discussion: <Robin_Watts> The problem is that we're getting stitch lines where the edges of the shading meet, and to fix that we need to push a transparency group before starting the mesh rendering. [10:12] <Robin_Watts> and ray_laptop said he'd do it because he had experience in that area.
Oops. I committed the fix (rev 12302) and forgot to close this bug.