On 2014-01-08 15:15-0800 phil rosenberg wrote: > I've just tried to use plshade, but with transparency - I want to plot transparent to black shading over the top of other shaded data. Unfortunately I'm getting not very attractive horizontal and vertical lines appearing at each of my x and y values. I guess these are because when plshade fills each section it's generating a 1 pixel overlap. This is using the wxWidgets driver. The lines appear in both the graphics context and agg backends. I just thought I'd email the list in case anyone had any suggestions for fixing this or knew if it happens in the other drivers? Unfortunately though I think I might have to just abandon this idea.
Hi Phil: The plshade and plshades functions always have such linear artifacts when creating a gradient because there is fairly coarse interpolation going on with no knowledge of the underlying grid of pixels. So I suggest you use plgradient instead to apply a native linear transparent gradient on top of another plot. (See e.g., http://plplot.sourceforge.net/examples-data/demo30/x30.02.png, for example of the sort of result that can be obtained for that case for the pngcairo device.) In contrast to the nice-looking cairo, qt, and svg device driver results for page 2 of example 30, the corresponding wxwidgets device results currently look quite bad (lots of vertical and horizontal lines). The reason is that device driver currently does not have a native gradient method implemented so plgradient falls back to using the plshades equivalent of a linear gradient which has all the linear artifacts alluded to above. So following the above advice to switch to plgradient will require some additional modest development effort on your part to get a good-looking result for the wxwidgets device driver. You will need to modify that device driver (following what is done for the cairo, qt, or svg device drivers) to provide native linear gradient support based on the linear gradient capabilities provided by the wxwidgets library (e.g., CreateLinearGradientBrush). Making such a wxwidgets change has been on my (very) long-term agenda, but I am not really that familiar with either the wxwidgets devices or the wxwidgets library so I would be happy to turn over responsibility for implementing this wxwidgets device driver change to you. 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); the Time Ephemerides project (timeephem.sf.net); PLplot scientific plotting software package (plplot.sf.net); 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 __________________________ ------------------------------------------------------------------------------ CenturyLink Cloud: The Leader in Enterprise Cloud Services. Learn Why More Businesses Are Choosing CenturyLink Cloud For Critical Workloads, Development Environments & Everything In Between. Get a Quote or Start a Free Trial Today. http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.clktrk _______________________________________________ Plplot-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/plplot-devel
