Thanks so much John! That does the trick. I'm just a new user of mpl, so your question about whether the default behavior of draw should be changed is probably "above my pay grade." I just don't know the API well enough to comment intelligently about it. That said, I would suggest that this behavior be documented (either in the tutorial page I originally accessed, the documentation for "canvas.draw()", both locations, or some other appropriate place).
Thanks again from a very satisfied mpl user, Brian John Hunter-4 wrote: > > On Fri, Feb 26, 2010 at 5:14 PM, brianjpetersen > <brianjpeter...@gmail.com> wrote: >> >> Hi All, >> >> I'm a new matplotlib user on a Windows XP machine running mpl0.99.0 under >> Python 2.5. I'm using the default rc file. >> >> While reading through the excellent matplotlib "how-to" tutorial >> (http://matplotlib.sourceforge.net/faq/howto_faq.html), I came across two >> useful scripts: one to save a figure with a transparent background, and >> one >> to resize axes automatically so that labels aren't cut off. I was able >> to >> run both these examples given on the "how-to" successfully. >> >> However, I ran into trouble when trying to combine them as follows: >> >> ===== >> >> import matplotlib.pyplot as plt >> import matplotlib.transforms as mtransforms >> >> fig = plt.figure() >> ax = fig.add_subplot(111) >> ax.plot(range(10)) >> ax.set_yticks((2,5,7)) >> labels = ax.set_yticklabels(('really, really, really', 'long', 'labels')) >> >> def on_draw(event): >> bboxes = [] >> for label in labels: >> bbox = label.get_window_extent() >> # the figure transform goes from relative coords->pixels and we >> # want the inverse of that >> bboxi = bbox.inverse_transformed(fig.transFigure) >> bboxes.append(bboxi) >> >> # this is the bbox that bounds all the bboxes, again in relative >> # figure coords >> bbox = mtransforms.Bbox.union(bboxes) >> if fig.subplotpars.left < bbox.width: >> # we need to move it over >> fig.subplots_adjust(left=1.1*bbox.width) # pad a little >> fig.canvas.draw() >> >> return False >> >> fig.canvas.mpl_connect('draw_event', on_draw) >> >> plt.savefig('test.png', transparent=True) >> >> ===== >> >> In this case, the saved png file is transparent, but the original set of >> axes, labels, and plot are visible as well (basically, I have two >> identical >> plots shifted over one another on a transparent background). >> >> Is there a way to suppress the original output (something akin to >> "fig.canvas.erase()" or "fig.canvas.clear()", but I can't seem to figure >> it >> out) so that the output png only shows the shifted axes and not both >> sets? > > Interesting! That one really surprised me. It turns out mpl is not > clearing the pixel buffer from the previous draw command. Normally > you don't see this because the call to draw the figure.patch blanks > out the pixel buffer with the background color, but since your figure > patch is transparent you can see the legacy. A call to > renderer.clear() before drawing again will erase the old image > (perhaps we should be doing this by default?) > > import matplotlib > matplotlib.use('Agg') > import matplotlib.pyplot as plt > import matplotlib.transforms as mtransforms > > fig = plt.figure() > ax = fig.add_subplot(111) > ax.plot(range(10)) > ax.set_yticks((2,5,7)) > labels = ax.set_yticklabels(('really, really, really', 'long', 'labels')) > > def on_draw(event): > bboxes = [] > for label in labels: > bbox = label.get_window_extent() > # the figure transform goes from relative coords->pixels and we > # want the inverse of that > bboxi = bbox.inverse_transformed(fig.transFigure) > bboxes.append(bboxi) > > # this is the bbox that bounds all the bboxes, again in relative > # figure coords > bbox = mtransforms.Bbox.union(bboxes) > if fig.subplotpars.left < bbox.width: > # we need to move it over > fig.subplots_adjust(left=1.1*bbox.width) # pad a little > fig.canvas.get_renderer().clear() > fig.canvas.draw() > > return False > > fig.canvas.mpl_connect('draw_event', on_draw) > > plt.savefig('test.png', transparent=True) > > > JDH > > ------------------------------------------------------------------------------ > Download Intel® Parallel Studio Eval > Try the new software tools for yourself. Speed compiling, find bugs > proactively, and fine-tune applications for parallel performance. > See why Intel Parallel Studio got high marks during beta. > http://p.sf.net/sfu/intel-sw-dev > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/matplotlib-users > > -- View this message in context: http://old.nabble.com/Transparency-with-fig.canvas.mpl_connect-tp27724532p27738002.html Sent from the matplotlib - users mailing list archive at Nabble.com. ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
