Re: [Plplot-devel] x20c.c

[Andrew R. <ar...@ge...>]

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=20
>libraries that may not be available on some other systems. In the=20
>first place, unix is not linux, plplot runs also on Macs and=20
>MSWindows, and the purpose of a demo is just showing a capability.=20
>That's the reason why I spend some time coding the reading of the=20
>image, instead of just calling a library. (After all it looks like=20
>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.=20

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