[ 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. -- 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
