** Description changed: + [ Impact ] + + OpenSlide (libopenslide0 in Ubuntu) uses Cairo as its rendering backend, + always with CAIRO_OPERATOR_SATURATE and sometimes with subpixel + positioning (when reading certain file formats), and Cairo in turn + invokes this code. As a result, some slides incorrectly render with + large blank spaces and with some pixels rendered on top of other pixels. + This effectively makes OpenSlide unusable for several of the file + formats it supports. No workaround is believed possible within the + OpenSlide codebase. + + [ Test Plan ] + + Compile and run the pixman.c test program uploaded to this bug. It + should report "OK". + + [ Where problems could occur ] + + Problems would show up as incorrect pixel output from software that + renders via Cairo or pixman. + + [ Other Info ] + + While I'm not a pixman expert, it appears that the change should only + affect the broken code path, and it seems unlikely that anything else + depends on the incorrect math fixed by this patch. This bug hasn't + previously been reported in Ubuntu, which may imply that this code path + is not exercised by other packages in the distro. + + The affected source file has had no further commits upstream since this + patch was applied in April 2019, and some basic commit grepping didn't + turn up any followup fixes elsewhere in the tree. + + [ Original message ] + pixman 0.38.4-0ubuntu1 in focal (and actually pixman 0.38.x generally) has a regression that causes incorrect rendering in some circumstances. This can be triggered by the use of cairo with CAIRO_OPERATOR_SATURATE and subpixel positioning, and causes OpenSlide <https://openslide.org/> to produce incorrect output. The attached test program will print "Failed" if the bug exists, or "OK" if it doesn't. This is fixed upstream in https://gitlab.freedesktop.org/pixman/pixman/-/commit/8256c235, which is in pixman 0.40.0. See https://github.com/openslide/openslide/issues/278 for more context.
** Also affects: pixman (Ubuntu Focal) Importance: Undecided Status: New ** Changed in: pixman (Ubuntu) Status: New => Fix Released ** Changed in: pixman (Ubuntu Focal) Status: New => Triaged -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to pixman in Ubuntu. https://bugs.launchpad.net/bugs/1988796 Title: Incorrect rendering triggered by cairo CAIRO_OPERATOR_SATURATE with subpixel positioning To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/pixman/+bug/1988796/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp