pcolormesh is outputting the data as vectors, since the mesh can be non-rectilinear, that's really the only thing that PDF supports. Besides, that's the only way to get a truly resolution-independent PDF. Since imshow is limited to uniform, rectilinear images, and PDF has built-in support for those, the file is much smaller and the drawing more efficient.
That said, there has been for some time experimental functionality to support drawing some elements "pre-rasterized" (meaning as images) to save on file size. This is actually already working in some backends (including PDF), it just hasn't been exposed to the user in a nice way yet. Eric Bruning had an elegant solution to add pre/post draw callbacks that would have really helped with this [1], but I don't know where all that ended. It would be great to pick that ball up and get it going again. If nothing else, it should be an easy fix to add a "rasterized" kwarg to pcolormesh -- but I don't recall if that's the interface that we arrived at the last time this came up. [1] http://www.mail-archive.com/[EMAIL PROTECTED]/msg03490.html Cheers, Mike Jose Gómez-Dans wrote: > Hi, > In a previous email I pointed out that I was having problems with pcolormesh > output as a PDF: the files are really big and impractical even for smallish > arrays (1000x1000 pixels). I don't have that problem using imshow, which > presumably resamples the image or somesuch wizardry :) Here's an example > > import pylab > data = pylab.randn((512*512)).reshape((512,512)) > #First imshow. I use the dpi keyword "just in case" > pylab.imshow ( data, interpolation='nearest') > pylab.savefig ("/tmp/imshow_72.pdf",dpi=72) > pylab.savefig ("/tmp/imshow.pdf") > #Now pcolormesh > pylab.pcolormesh ( data ) > pylab.savefig ("/tmp/pcolor_72.pdf",dpi=72) > pylab.savefig ("/tmp/pcolor.pdf") > > This results in the following files: > 166K /tmp/imshow_72.pdf > 307K /tmp/imshow.pdf > 2.6M /tmp/pcolor_72.pdf > 2.7M /tmp/pcolor.pdf > > So: in the imshow case, the dpi keyword makes a difference (good!), but if > you > compare the pcolormesh and imshow filesizes you immediately notice a large > difference. The rendering of the pcolor files is also very slow, line-by-line > sort of thing. I presume that the different patches are stored as vectors, > and that's why there's no change with setting dpi to 300 or to 72. > > Is this the expected behaviour? > Thanks, > J > > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/matplotlib-users > -- Michael Droettboom Science Software Branch Operations and Engineering Division Space Telescope Science Institute Operated by AURA for NASA ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
