El Diumenge, 12 de febrer de 2012, a les 08:43:58, Thomas Freitag va escriure: > Hi! > > As announced, here my overprint patch. It is an enhancement patch, a > merge fix and a bug fix in one: an enhancement, because it now completes > the implementation overprint mode and devicen in postscript, a merge > fix, because it fixes some bugs in the overprint implementation in > splash of xpdf 3.0.3 and has now the complete functionality (and more!) > of my implementation back again and a bug fix, because it fixes the use > of splash cmyk in postscript which never had worked. > > 1. Overprint implementation in postscript > To have a complete overprint implementation in the (pure) postscript > device there were just two things missing: overprint mode and the > implementation of the DeviceN colorspace in PostScript. I double checked > my implementation with the Ghent Test Suite with GhostScript (device > pdfwrite) and Acrobat X distiller, and all the tests now succeeds, > either in Acrobat X distiller or in GhostScript. As overprint is a > device dependent feature, it is up to the output device if it supports > overprint and what features of overprint are supported, and often You > have various configuration possibilities there. Nearly all PostScript > output of the Ghent tests show now the desired results if converting it > back to PDF with ghostscript pdfwrite, the implementation in ghostscript > is complete. On the other hand a few tests failed when using Acrobat X > distiller, all of them with the overprint mode switch. Funny, because > overprint mode 1 is often also called the illustrator overprint mode > because it was introduced by illustrator, but probably the destiller > only handles EPS correctly which comes from illustrator :-) > > 2. Overprint implementation in postscript if using splash rasterization > Of course the postscript overprint implementation will only work if > pdftops doesn't decide to use splash to rasterize it because of the use > of transparencies in the PDF. But because overprint is device dependent > I decided to spend an additional parameter "overprint" to pdftops > (simular to pdftoppm). Switching it on (only available if compiled with > SPLASH_CMYK, because overprint is only in CMYK colorspace showable) will > use the overprint implementation in splash also if rasterizing the PDF. > > 3. Overprint implementation in splash > The overprint implementation in splash now uses the better designed > interface of xpdf and therefore now also works in transparency groups. > Thanks to the developper team of xpdf. I just fixed a small bug in it, > where it defies the technical specification. Of course it is still in > the nature of the splash implementation that it fails if CMYK values > should overprint spot colors, because spot colors are converted > immediately in their CMYK alternates. And in the implementation of > overprinting spot colors over CMYK colors I made a small assumption to > get it running which causes undesired results if this assumption fails, > but I didn't want to implement more and more configuration switches. I > still plan to implement a DeviceN output in splash and make a complete > implementation there, but this is of course a bigger task (but doable). > The overprint switch in pdftoppm is still only available if compiled > with the SPLASH_CMYK directive. > > If someone wants to know more about overprint, just contact me directly. > Then I'll send the technical papers and/or hints to specifications.
Pushed to master. Albert > > Cheers, > Thomas _______________________________________________ poppler mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/poppler
