Hello to everyone,
I'm (still) working on an application used for plotting graphs and I've come across one not very pleasant speed issue regarding drawing rectangles -- the larger rectangle, the slower drawing speed.
My application should be able to handle millions of values, but I've found out, that it takes very long to draw barplot or similar plot containing rectangles (drawing ellipse is faster)... When drawing small rectangles (4x4 pixels), it is quite fast (250 000 rects/6sec), but then I tried to draw 250 000 rects, each 200x200 pixels large, and it took almost 15(!) minutes to complete this task... (same code and image size, just increased rects sizes)
Do you know any workaround for that? Or do you have any suggestions how to make drawing faster?
Another question: I'm drawing on QImage, do you think that new (since Qt4.2) graphic canvas would be better for drawing these kind of plots?
Thanks for every answer.
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