Re: [matplotlib-devel] New backend API

[Darren D. <dd...@co...>]

On Monday 03 April 2006 11:16 am, John Hunter wrote:
> >>>>> "Darren" == Darren Dale <dd...@co...> writes:
>
>     Darren> I'm having second thoughts about the wisdom of having
>     Darren> postscript handle the transforms. With the new API, I run
>     Darren> backend_driver.py and get a file called
>     Darren> axes_demo_PS.ps. On my machine, it takes about 10 seconds
>     Darren> to open this file if it was created with the new API. If I
>     Darren> mask draw_markers and recreate the postscript file, it
>     Darren> loads instantly.
>
> So you think the performance hit is caused by gs (or whatever viewer
> you are using) by the postscript engine doing the transformations?  It
> surprises me that this would be so inefficient.
>
> We have the option of doing the transformations in the ps backend...

I think there are two issues here. The postscript interpreter doesnt like to 
stroke long paths. If I break the path into 50 point chunks instead of 1000 
point chunks, I see an improvement.

Also, if I do the transform in backend_ps, instead of passing it to the 
postscript interpreter, I see a big speedup at render time. Right now I am 
doing this transform by hand:

a,b,c,d,tx,ty=vec6
xo = a*x+c*y +tx
yo = b*x+d*y + ty
x,y = xo,yo

Is there a better way to do this? I thought I could simply call numerix_x_y, 
but that function is not compatible with nonlinear transforms (returns a 
domain error if one of the axes is log-scaled).

Thanks,
Darren