Faster Text drawing needed

Original report at SourceForge, opened Wed Mar 21 08:03:30 2007

Drawing of plots with multiple matplotlib.Text instances is so slow as to be unusable for some applications, such as realtime multiple sequence alignment rendering/viewing (see attachment for a pylab example, resize plot window to see effect).

Some layman's thoughts:

Would it be possible to speed things up by implementing some kind of Text Collection?
Is antialiasing involved? An option to turn it off would be nice in that case.

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On Thu Sep 6 16:07:54 2007, mdboom wrote:

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It appears that the text is re-rendered to a newly allocated buffer each time the text is drawn. Perhaps some caching of text elements would help.

(Mostly just making a note of it for someone else to work this through, or until I have the time.)

SourceForge History

On Wed Mar 21 08:03:30 2007, by yohell: File Added: 221568: test.py

This is the OP's attachment:

import random
import pylab
aas = "ACDEFGHIKLMNPQRSTVWXY-"
fig = pylab.figure()
xmax = 100
ymax = 50
for iX in range(xmax):
    for iY in range(ymax):
        pylab.text(iX + 0.5,
                   iY + 0.5,
                   random.choice(aas),
                   family = 'sans-serif',
                   size = 6,
                   horizontalalignment = 'center',
                   verticalalignment = 'center')
pylab.xlim(0, xmax)
pylab.ylim(0, ymax)
pylab.savefig("test.png")

+1 in favor of adding a TextCollection class to matplotlib

There's really two problems here:

Rendering text with the Agg backend is slow because it assumes the text may be rotated, which requires an affine transformation and filtering at each pixel. I have a faster text blitting implementation (for non-rotated text only) on my 347_fast_text branch. This change provides about a 20% speedup on this example. Unfortunately, this causes a lot of the regression tests to now fail since the text is crisper (and theoretically more correct). I will need to wade through the regression test results and update baseline images before merging this.

The need for a TextCollection remains, though from profiling, it's not clear that the lack of one is the bottleneck here.

@mdboom

@mdboom: Seems like a 20% speedup & crisper text are worthwhile pursuits. Do you have any update on this? Are you considering making a PR out of the change?

This would be really nice. After doing some profiling text rendering and complicated tick handling are main reasons for mpl slowness.

Fix matplotlib#347: Faster text rendering in Agg

Merge pull request #5361 from mdboom/fast-text

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Faster Text drawing needed #347

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On Thu Sep 6 16:07:54 2007, mdboom wrote:

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Faster Text drawing needed #347

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SourceForge Comments

On Thu Sep 6 16:07:54 2007, mdboom wrote:

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mdboom commented on Jun 21, 2011

butterw commented on Jun 21, 2011

mdboom commented on Jun 22, 2011

pelson commented on Jun 30, 2012

Tillsten commented on Sep 30, 2015

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