Michael Droettboom wrote: > This is a long-standing known issue with the contour code. The > contouring library we are using (in cntr.c) was written for a graphics > library that did not support compound paths, so to draw a donut-shaped > objects it creates "cut paths" from the inner to outer edge. A number > of the matplotlib developers have taken stabs at changing this behavior > over the years, but it is a very opaque chunk of code, and none of us > have managed it without introducing new more serious errors. A fresh > set of eyes may be able to sort it out, and we do have compound path > support in all backends (save the mostly obsolete Gdk) now. Replacing > the contouring code with something else that is license-compatible is > also an option, but I wasn't able to find anything suitable last time I > looked (which was a long time ago now).
I have been looking about every 6 months for years, with absolutely no success. There are remarkably few filled-contouring codes (or detailed algorithm descriptions) out there, under any license. Note also that the code Matlab uses (or at least used a long time ago when I last looked) handles the problem by layering the contour patches, not by leaving holes, so it is an example of a class of algorithms that would not work with non-unit alpha. I have also thought a bit about manipulating the paths generated by the present code to remove the cuts, or manipulating the non-filled contour output to generate patch boundaries, but I haven't gone into it deeply. I suspect it would quickly become very complicated. And, on top of all that, even if we solved the cut problem, there would still be backend-dependent artifacts involved in rendering the boundaries. Eric > > Cheers, > Mike > > Joseph Smidt wrote: >> I am making contourf plots with some transparency as I want to >> eventually overlay such plots. When I plot such plots I see artifacts >> or lines that shouldn't be there as seen here: >> http://josephsmidt.googlepages.com/ex.png >> >> Is this a bug or am I plotting incorrectly? My script is here: >> http://josephsmidt.googlepages.com/plotex.py and the data needed for >> the plot is here: http://josephsmidt.googlepages.com/exCHI.txt >> >> However, the relevant part of the code for plotting I'll just cut and >> paste here: >> >> levels = [x0, x1, x2, x3] >> contourf(Y,X,transpose(CHI),levels,alpha=0.7) >> show() >> >> Thanks. >> >> Joseph Smidt >> >> >> > ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
