Re: Simplified processing of image and rgbimage plots

[Ethan A M. <merritt@u.washington.edu>]

On Sunday 19 November 2006 05:47 am, Petr Mikulik wrote:
> >> This extends the capabilities of svg, xfig, and maybe other terminals.
> >>
> >> The specialized code for image handling could be removed from gd.trm, for
> >> instance. Also x11. Is this worth doing?
> 
> Do you really mean to remove the term->image() routine??? Definitely no, the 
> processing is several orders of magnitude slower ... try to draw a 1024x1024 
> image with pm3d and with image. Terminal-specific term->image() is the 
> proper way.

It may seem counter-intuitive, but in fact the RGB polygon processing is
just as fast as the term->image() processing, at least for gd.trm.
Here is a timed benchmark run using a 800x600 image for the test script

  set term png truecolor size 1024,768
  set output 'junk.png'
  plot 'bench.avs' binary filetype=avs with rgbimage
  replot
  [... 10 plots total]
  replot

time ./gnuplot bench.gnu  (average of 5 runs)
  16.785u 0.509s 0:17.31 99.9%    0+0k 0+0io 0pf+0w

same thing except "with rgbimage generic"
  16.672u 0.572s 0:17.18 99.4%    0+0k 0+0io 0pf+0w



The generic code is significantly slower (4-5X) for x11, but I think that
is a matter of the transfer time through the pipe for a description that is
less compact (30MB vs 2.9 MB).  This difference could be reduced by switching
to a binary protocol for transmitting RGB color + polygon down the pipe.




x11 with rgbimage
  6.331u 0.675s 0:07.05 99.2%     0+0k 0+0io 0pf+0w
x11 with rgbimage generic
  28.418u 17.907s 6:37.59 11.6%   0+0k 0+0io 0pf+0w


-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742