Please download file from: http://data.bonprixflyers.com/rjuploader/2012-11-14/32730/32731/1352913166086_0013985_1_A5_36_pp_proof.pdf For example please try render page 5. The problem is missing rendering image under text "Le Livert d'Information". See attached screenshots.
Created attachment 9094 [details] mupdf render page 5
Created attachment 9095 [details] acrobat render page 5
Created attachment 9096 [details] ghostscript render page 5
I bet the images (one per line it seems) which make up the mis-rendered section are in a different cmyk color space than the rest of the page. I expect that enhancing mu to use lcms2 would fix this one.
This is not problem with diffrent color space of images, etc. but with antialiasing. Please try to render page 5 with diffrent values of antialiasing level, then you see diffrent results.
> try to render page 5 with different values of antialiasing That is an interesting effect. Perhaps it is a downscaling issue, then? It does look better at 300 dpi than at 100 dpi.
The problem with this file is that the inset image is actually several hundred 1 pixel high images stacked on top of one another. Ordinarily we cope with this quite well, but the fact that the images are rotated hurts us a bit. We'd even cope with this, but the real killer is that each of these images has a 1 pixel high clip path, set for it, and these too are rotated. MuPDF renders these clip paths by rendering them to a greyscale pixmap and then masking the contents through these. This gives us nice antialiasing of clips - but in this case results in the contents coming out too light. The solution I have here involves changing MuPDF to render all clip regions without antialiasing. This means that every pixel in the clip will either be full on or off. I believe this is more in keeping with how Acrobat works. We are evaluating whether this will have an overly adverse effect on other files now.
It does indeed cause other files to look nasty. Continuing to think about this, but I suspect this will be left as a 'looks bad due to stupid PDF file construction' case for a while.