[Matplotlib-users] Help needed: Rendering of multiple text labels is very slow.

[Joel H. <yo...@if...>]

Hi!

I'm using matplotlib and pygtk to write a viewer for multiple sequence 
alignments. (Big matrices (~100x1000) of characters, usually colored by 
cell according to chemical properties). Now I've run into trouble since 
the rendering of the actual characters is very slow. I have included a 
small example that illustrates this. Set SHOW_LETTERS = False to see the 
change in rendering speed. The difference is even greater when using 
real data, so I would very much appreciate suggestions as to how I could 
improve it.

My strategy:
I create an image with the same dimension as the msa, and where each 
pixel is colored according to properties of the corresponding character 
in the msa. I plot this in the background of the figure using imshow(). 
At each redraw (refresh, resize, zoom...) I determine the size that each 
image pixel occupies at the current canvas size, and pick a font where 
one letter will fit inside this square. Then I put the corresponding msa 
  letter into this square using text()/add_artist().

Would it be possible to use only one Text instance that would hold all 
letters, and somehow stretch that to the desired size? If so, could I 
expect better performance?

Does anyone have a better idea?

Thanks for an awesome plotting package!
/Joel Hedlund