As Werner recently showed for the cairo driver, boundary stokes on adjacent filled completely opaque regions are a great idea to keep background from leaking through at the join due to AA effects. Examples 8, 16, and 20 look much better (in fact, perfect) for device pngcairo due to Werner's change so I have turned on AA for those examples (revision 9231) for our website (the next time we generate it).
Example 30 is a different story, however, because the adjacent filled regions in the second page are partially opaque, and in that case alone, overlapping boundary stokes create a bad composite opacity that produces a nasty looking abrupt increase in opacity at the edge of each boundary. (In the example 30, page 2 case, it looks like 100 horizontal lines because the opacity gradient is implemented with 100 separate plshades regions.) Thus, I turned off boundary stroking of filled regions for the svg driver when the opacity was less than 0.99, and the example 30 svg page 2 results look much better (but still not perfect) because of this change. Example 8, 16, and 20 are unaffected because the fills for those examples are completely opaque (opacity of unity). Werner, would you be willing to make a similar change to cairo.c to see if it produces better-looking example 30, page 2 results? (I tried to make that change myself, but I could not get it to work properly because I was having trouble following the logic of how to tell libcairo how to drop the boundary stroke on the filled region. I didn't get the effect I wanted and the colours of the background squares became all the same so I must have been doing something wrong. Alan __________________________ Alan W. Irwin Astronomical research affiliation with Department of Physics and Astronomy, University of Victoria (astrowww.phys.uvic.ca). Programming affiliations with the FreeEOS equation-of-state implementation for stellar interiors (freeeos.sf.net); PLplot scientific plotting software package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project (lbproject.sf.net). __________________________ Linux-powered Science __________________________ ------------------------------------------------------------------------------ _______________________________________________ Plplot-devel mailing list Plplot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/plplot-devel
