Re: [Plplot-devel] x20c.c

[Alan W. I. <ir...@be...>]

My motivation here is to have a good-looking demo.  Obviously something is
not correct about the current method of reading in lena.pgm since the other
parts of the demo show that plimage works well, and if I look at lena.pgm
directly with kview, that is one heck of a good-looking image....;-)
Probably, one could fix up the current pgm input, but I don't see much poin=
t
to this reincarnation of the libpgm library if we can satisfy the valid
cross-platform concerns that you and Joao have expressed another way.

Thus, Andrew, I like your suggestion for using png format for our standard
input format and using libgd to read it since both are cross-platform. Also
as you point out, on Linux the user can convert anything to png format usin=
g
the netpbm package.  I have already used that package in the following way:
anytopnm < lena.pgm | pnmtopng > lena.png. The high-quality result was
indistinguishable from the original even at high magnification. Thus, I
would like to concentrate now on getting proper input of png images for
x20c.c so we can have a good-looking result.

Now the big question for Andrew: would you be willing to programme png inpu=
t
to x20c.c using libgd (version 2)?  I am willing to do this myself starting
tomorrow using libgd version 2.0.1 that is on my Debian woody system, but i=
t
might take me a while and with your C skills it might be trivial for you to
do. Even if you provide just the bare bones of the png reading programme, i=
t
would help me get a much quicker start.  Let me know what you decide.

Alan

email: ir...@be...
phone: 250-727-2902=09FAX: 250-721-7715
snail-mail:
Dr. Alan W. Irwin
Department of Physics and Astronomy,
University of Victoria, P.O. Box 3055,
Victoria, British Columbia, Canada, V8W 3P6
__________________________

Linux-powered astrophysics
__________________________

On Tue, 27 Nov 2001, Andrew Roach wrote:

> At 12:09 AM 27/11/01 +0000, Jo=E3o Cardoso wrote:
> >On Monday 26 November 2001 20:43, Alan W. Irwin wrote:
> >| I have a suggestion.  Why not add a function to this demo to input
> >| various image formats and extract the information required by
> >| plimage? Right now, there is rudimentary support for reading ppm
> >| images from x20c.c, and I suggest replacing this with the
> >| appropriate calls to libpbm, libpgm, libpnm, or libppm.
> >
> >I have no strong objections to that, except that x20c will depend on
> >libraries that may not be available on some other systems. In the
> >first place, unix is not linux, plplot runs also on Macs and
> >MSWindows, and the purpose of a demo is just showing a capability.
> >That's the reason why I spend some time coding the reading of the
> >image, instead of just calling a library. (After all it looks like
> >that I have objections ;-)
>
> I am inclined to agree with Joao here with regards to the concerns of
> having those libraries available on other systems. I confess that have
> never looked to see if libpbm etc... are available for DJGPP, thought I
> expect they would be in some form. What would prove more difficult is
> evoking external image converter programs on other platforms. I
> /personally/ think it is perhaps best left as is, with the image command
> just rendering a user-supplied bitmap, and leaving the supply/generation =
of
> that bitmap up to the user.
>
> However, if we do want to have INTERNAL loading of bitmaps (not just
> user-provided ones) there are some other things to consider.
>
> With respect to linking to libpbm etc... and letting them do the image
> reading, and then using external conversion programs to change the format
> into pbms etc... that almost SETS the preferred image format to the pbm
> family. Why pick that format over any others ? It is a very easy one to
> read in a demo like X20c, but isn't necessarily the most flexible or
> acceptable image format out there. There is almost zero use on platforms
> outside on unix/linux. We could just as easily (and perhaps more
> logically), link to libgd, libjpeg, & libpng then read either JPEGs and/o=
r
> PNG images as the "raw format" supported by plplot, using external image
> converters to convert other formats (ie the pbm family) to PNGs. In some
> respect, especially for DOS, windows, and MACs, PNGs have more use,
> flexibility, and acceptance than the pbm family. Just a thought...
>
> - Andrew
>
>
>
>
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