[Matplotlib-users] Bliting speed improvment patch (QT4Agg backend) + example of sliding demo

[Laurent D. <lau...@gm...>]

Hi there,

Finally with lot of try I've finally managed to make blitting of a cmap
working.
I've also patched QT4agg backend, to make a redraw immediately.
(replaced self.draw by self.repaint)
In my current project I was able to stream a 655KB network stream, do
demodulation of an IQ stream and display the spectrogram in real time (4096
pixel per 1024) with matplotlib and QT4 backend, thx to the patch + blitting
example attached.

Without patch, the refrech was veeery long. (waiting for QT loop to execute
code wen it wanted.)
And do NOT always work. If you've got a powerfull pc you've got chance to
see only white background...
(or simply the loop timer to 0, you will see that without patch blit does
not work).

Only tested under windows currently, 'cause my project is on windows
currently...

There is one bug in the example, that I didn't manage to correct yet.
Depending on screen resolution, the color of the cmap blitted area can be
kind of alpha'ed. (that is look like a little bit transparent...) , Any idea
on the root of this issue?

By the way to make the example work I needed to do this:
        self.ax2.draw_artist(self.line2)
        self.blit(self.ax2.bbox)
        self.restore_region(self.background2)

that is blit before restore... don't understand why yet.

Any comment welcomed.

Is there any chance, after review, to find a way to include this in main
trunk?
What do think about this?

Cheers,
Laurent