Title: Fixed background colour of PNGs saved with a non-zero opacity. by pelson · Pull Request #1868 · matplotlib/matplotlib · GitHub
Open Graph Title: Fixed background colour of PNGs saved with a non-zero opacity. by pelson · Pull Request #1868 · matplotlib/matplotlib
X Title: Fixed background colour of PNGs saved with a non-zero opacity. by pelson · Pull Request #1868 · matplotlib/matplotlib
Description: The following code (a derivative of http://stackoverflow.com/questions/15691297/how-to-directly-set-alpha-channel-value-for-matplotlib-figure-background-colour) was producing a png with an unexpected background colour. This PR fixes the problem so that the background colour of a PNG is as expected (and consistent with SVG). import matplotlib.patches as mpatches from matplotlib.image import imread from matplotlib.backends.backend_agg import FigureCanvasAgg as FigureCanvas from matplotlib.figure import Figure fig = Figure() canvas = FigureCanvas(fig) fig.set_facecolor('black') fig.patch.set_alpha(0.3) fig.patches.append(mpatches.CirclePolygon([200, 200], radius=80, facecolor='red')) print 'Target: ', fig.patch.get_facecolor() fig.savefig('test_fig.png', facecolor=fig.get_facecolor(), edgecolor='none') print 'Result: ', tuple(imread('test_fig.png')[0, 0]) Yields: Target: (0.0, 0.0, 0.0, 0.3) Result: (0.69803923, 0.69803923, 0.69803923, 0.3019608) After this change, the result is: Target: (0.0, 0.0, 0.0, 0.3) Result: (0.0, 0.0, 0.0, 0.3019608) I'm not certain why the value is not exact, but I'm comfortable with the approximation. There remains a problem with PDF creation (& other backends not tested). I do not propose to fix the PDF issue in this PR.
Open Graph Description: The following code (a derivative of http://stackoverflow.com/questions/15691297/how-to-directly-set-alpha-channel-value-for-matplotlib-figure-background-colour) was producing a png with an unexpect...
X Description: The following code (a derivative of http://stackoverflow.com/questions/15691297/how-to-directly-set-alpha-channel-value-for-matplotlib-figure-background-colour) was producing a png with an unexpect...
Opengraph URL: https://github.com/matplotlib/matplotlib/pull/1868
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