Re: [gnuplot]: set term size & ConTeXt

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

On Monday 19 June 2006 01:03 pm, Daniel J Sebald wrote:
> Daniel J Sebald wrote:
> > Nothing like cow plots to motivate someone from the dairy state. 

Moo.

> And as for command line syntax, we'll have "with rgbaimage" in a
> fashion similar to "rgbimage"?  

Remember that the decision whether to use transparency is a
separate question from whether the external file contains an alpha
channel.  That is,  
   `plot "foo" binary filetype=avs with rgbimage`
already handles an input stream containing an alpha channel, but
it is just discarded rather than being used in plotting. In the
case of AVS, it *always* has an alpha channel. But I'm not sure
how you generalize it to other input file types.

> What about the possibility of mapping  a particular pixel value
> to transparent, as I imagine a lot of glyphs might do?

That's part and parcel of the same issue. The input file might
not contain a separate alpha channel, but we might nevertheless
be able to generate one on the fly.

> Then again, a lot of palette based images don't have alpha
> blending... Am I worrying about a non-problem?

No. It's a real problem. There has to be a mechanism to specify
how many channels are to be read from the input, and a separate
mechanism to specify how many channels are used in plotting.

The latter may be as simple as a keyword "transparent".
E.g. plot the same file twice, with and without transparency:

  plot "foo" binary filetype=avs with transparent rgbimage
  plot "foo" binary filetype=avs with rgbimage

Or, following your suggestion, it could instead be

  plot "foo" binary filetype=avs with rgbaimage
  plot "foo" binary filetype=avs with rgbimage

In either case the command is controlling whether the alpha
channel is used on *output*.  The input in this case always
has an alpha channel, although that would not be true in general.

	All of this for post-4.2, of course.
	Let's defer detailed discussion til then

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