On Mon, 22 May 2006, Andre Wobst wrote:

> Hi,
>
> On 22.05.06, Arnd Baecker wrote:
> > > BTW: Why don't you use larger bitmaps (covering the
> > > whole graph)? Even when you than need to add the bitmap data for all
> > > the white area (and as long as you don't need that area to be
> > > transparent), I expect this to be much smaller in the result and
> > > faster too!
> >
> > Sorry, but I don't understand -
> > A couple of plots I have look (in principle) like:
> >   http://www.physik.tu-dresden.de/~baecker/python/pyxgraph/array1.png
> > Internally the bitmap is obtained from a PIL array via
> >     im = Image.new("RGB",(w,h))
> >     im.fromstring(rgb.tostring())
> > where rgb is an (N, 3) arrray with the r, g, b colors.
> >
> > How would using a larger bitmap avoid the ASCII85 encoded streams?
>
> It would not avoid ASCII85 encoded streams. But although the bug seems
> to be in ghostscript for a long time already, it seems to be triggered
> in rare cases only. It just has been identified and fixed recently.
> But from what you've told me you stepped into the problem frequently.
> While this is not a problem at all, it is related to how you build
> your output. There's nothing wrong in building a lot of small bitmaps
> -- but larger bitmaps (even when most parts might be white) may still
> help you to further reduce your file size (and the rendering will
> probably also become faster).
> This was just a comment I wanted to make
> about why I guess you've seen the issue that frequently.

I think that this is more an effect of statistics - for example if I
generate a file with 3626 plots (of Husimi functions of a
quantum map - FWIW), then chances get pretty high that I will run
into the problem.

> > > Beside that I'm thinking about removing the ASCIIHexDecode again. It's
> > > a quick hack and only implemented for current stream binary inserts
> > > (not for storring data on the PS stack and for the palette of indexed
> > > images). We should either remove it once and for all or implement it
> > > properly. I strong +1 for removing it ... :-)
> >
> > So what is the alternative to ASCIIHexDecode when one has
> > ghostscript < 8.54?
>
> What a question.

Well, I just wanted to be sure that I don't miss a possible
alternative ;-)

> The alternative is to update ghostscript to a
> version, which doesn't show the bug ... :-)

Hmm, this might be an option for my own computer, and maybe one
(though with more effort ;-) for all  the machines in our group.
However, I clearly cannot upgrade ghostscript on any of
the computers of potential readers of my articles.

So therefore I would conclude that there is no alternative to
ASCIIHexDecode...

> The point is that we currently do not support the PSbinascii flag very
> well ... it's a hack (beside that it's not documented etc.) and we
> should get rid of it again ASAP (as we do now understand what was
> going wrong and since a proper solution).

OTOH, this seems the only solution to the original problem
as long as one cannot be sure that all readers will have
ghostscript>=8.54, so I am not so positive on removing it.

Best, Arnd


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