Re: [Plplot-devel] x20c.c

[<jca...@in...>]

On Tuesday 27 November 2001 07:35, Alan W. Irwin wrote:
| My motivation here is to have a good-looking demo.  Obviously
| something is not correct about the current method of reading in
| lena.pgm

Thus, lets correct it.

| 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 point to this reincarnation
| of the libpgm library if we can satisfy the valid cross-platform
| concerns that you and Joao have expressed another way.

There is no such reincarnation of libpgm in x20c.c. libpgm has=20
certainly much more functionalities than just reading "lena".

| Thus, Andrew, I like your suggestion for using png format for our
| standard input format

Do we have a standard [image] input format? That is another issue. As=20
Andrew said, there are two issues here: x20c.c and libplplot.

As libplplot currently has no API entries to reading/convert images,=20
x20c.c uses a fast and crude way of reading an image, with the=20
purpose of demonstrate a libplplot API. "lena" is generaly available=20
as jpeg. As I *didn't* want to use libgd to read jpeg, I converted it=20
to ppm, which is simple to read.

If we are willing to have image reading/convertion in libplplot, than=20
we must start thinking on what we want, why, implement it, and than=20
recode x20c.c to use and *demonstrate* the new libplplot capabilities.

But I don't think that plplot should have such image capabilities, as=20
there are enought good quality libraries for that purpose. Instead,=20
the user will write his program, read the image in whatever format he=20
desires, using the method or library he desires, transformate it in=20
whatever way he desires, and then call plimage() to draw it.

Thus, I think that one must correct the x20c.c *demo*, and eventually=20
discuss the image operations to add to plplot.

Joao

| 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 using 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 input 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 it 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, it 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/or
| > 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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