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Improve handling of alpha when saving to jpeg.#15437
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Temporarily changing the figure background and manually calculating the alpha-shading towards white is more low-level. It's harder to understand what's going on and it might be more susceptible of introducing bugs in the future.
Is the performance gain worth it?
| @@ -563,23 +563,26 @@ def print_jpg(self, filename_or_obj, *args, dryrun=False, pil_kwargs=None, | |||
| `PIL.Image.save` when saving the figure. These take precedence | |||
| over *quality*, *optimize* and *progressive*. | |||
| """ | |||
| FigureCanvasAgg.draw(self) | |||
| if dryrun: | |||
| return | |||
| # The image is "pasted" onto a white background image to safely | |||
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The comment needs to be adapted.
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well, this is still pasting the figure over a white background.
anntzer commentedOct 18, 2019 • edited
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edited
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Actually, another motivation for the change is to make buffer_rgba() return an array that can be directly passed to imsave() -- essentially doing the same thing as in#15435, but for jpeg. |
| @@ -563,23 +563,25 @@ def print_jpg(self, filename_or_obj, *args, dryrun=False, pil_kwargs=None, | |||
| `PIL.Image.save` when saving the figure. These take precedence | |||
| over *quality*, *optimize* and *progressive*. | |||
| """ | |||
| FigureCanvasAgg.draw(self) | |||
| # The image is "pasted" onto a white background to handle transparency. | |||
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I think the term "paste" is a bit misleading
| #The image is "pasted" onto awhite background to handle transparency. | |
| #Remove transparency by alpha-blending on an assumedwhite background |
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sure, sounds good, edited accordingly
We can compose the figure facecolor against a white background beforerendering the image, rather than after. This saves an image compositionstep.
Will this cause weird flickering on interactive views (maybe not regular figures that composite on white, but embedded/notebook/something else)? |
I'm not sure why it would? |
I was thinking of stuff like changing the DPI, but I see setting the canvas manager is handled in the call stack above this one. |
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We can compose the figure facecolor against a white background before
rendering the image, rather than after. This saves an image composition
step.
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