Benjamin Root <ben.r...@ou.edu> writes: >> It seems that savig a pcolor plot to a pdf format always includes >> gridlines, which isn't true for other output formats like png. The >> attached example demonstrates this problem. I've only tested this on >> version 1.1.1rc1. > > I have reported something like this before, and it seems that it is > dependent upon the PDF viewer and i's settings. Particularly, the > antialiasing settings. I have seen this with gs-based viewers. Have you > tried others?
I see gridlines in the resulting image in gs, xpdf Preview.app but not in Adobe Reader. When I zoom in Preview, the lines jump around a bit, and are always the same width on the screen regardless of zoom level. What gets drawn in this example is a lot of polygons, so that adjacent polygons share an edge with the exact same coordinates. The code fills the inside of each polygon, and apparently some rendering algorithms leave a minimal-width line between polygons. Making the polygons overlap by one pdf unit (1/72 of an inch) seems to make the lines go away at least in Preview. Making them overlap by 0.1 units does not help. I don't think this can be fixed purely in the pdf backend; it just gets a path collection and draws each polygon. I suppose pcolor would need to pad the polygons a little, but could it cause problems with other backends or use cases? (E.g. if you use alpha blending, neighboring rectangles might get gridlines of a darker color where they overlap.) I wonder if drawing zero-width lines between neighboring rectangles, e.g. taking the color always from the left or the upper rectangle, would work. In matplotlib a line of zero width means no line at all, but in the pdf file format it means a line of the smallest possible width, which might work well for filling in a missing line of that same width. This would need some kind of special-casing in the graphics context (because linewidth=0 means to not draw a line) so it's not completely trivial to try it out. A different approach would be to output a raster image from pcolor and render it with large pixels. I don't know how well that would work with Agg, though. -- Jouni K. Seppänen http://www.iki.fi/jks ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Matplotlib-devel mailing list Matplotlib-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-devel
