Nicu Buculei wrote:
I have a not very complex SVG (7 layers, under 20 blurred objects) and it proved impossible to export it as PNG at 1600x1200. CPU usage climbs to 100% (Athlon XP 1800+) and stay here, Inkscape becomes unresponsive. I had to kill it after 30 minutes. Exporting a thumbnail at 128x96 work OK, but the full image not.
The performance issue can be solved by using my patch that was mentioned earlier. But the file you attached exposes a additional problem related to the pretty huge amount of blur you're using.
It seems Inkscape doesn't respect the borders needed by the gaussian blur when they fall outside the bounding box of what is being rendered, giving incorrect results at the edges. I expect this is what causes bug 1588463 and when exporting this gives particularly nasty results as the output image is rendered in stripes of 64 pixels high...
The most straightforward fix would be to not clip the rendered area (at least not the borders needed by the gaussian blur) until the last moment. This would probably work reasonably well for solving bug 1588463, but it might make exporting even slower than it already is.
In any case, I tried making this work but somehow couldn't figure out how to do it correctly, so if anyone knows how to do this (or knows of a better way to fix this problem) that would be great. As far as I can see nr_arena_item_invoke_render is where the borders for gaussian blur are added to the rendered area and then clipped to a bounding box. My guess is that the following line shouldn't be there: nr_rect_l_intersect (&carea, &carea, &item->bbox); But simply commenting that out gives weird results (if I remember correctly the exported image got borders around it and the artifacts remained).
...
Is there a way for me to get the PNG? I guess I can leave it over night to export, but this is ridiculous for such a small and simple file.
I patched my Inkscape to use doubles in the IIR filter (I have updated the patch on SF) and set the stripe size to the entire image and that gives a good result (although I expect problems if the blurred parts of the image come too close to the edges). This isn't a complete solution yet though, so I haven't uploaded a patch for the larger stripe size. If you want you can send my the SVG and I'll render it for you, or I can send you a patch and you can compile Inkscape yourself (if you use Windows I can provide patched executable version of Inkscape).
BTW, enlarging the stripe size has a very nice effect on rendering time, when I first tried rendering redblur.svg (attached to the initial post) with the IIR patch it took slightly less than two minutes, with the entire image as one stripe it takes about ten seconds! (at 1600x1200)
So would it be an idea to make it possible to use larger stripes in any case? Especially since the current stripes seem pretty small, I rarely export an image larger than a few thousand pixels by a few thousand pixels, so a single stripe would be something like 64 to 256 KB, if they would be a hundred times as large my system still wouldn't mind a bit.
I could image a preference for setting the maximum size for a single slice for example (although it would hard to account for the enlargement needed by blur mentioned above).