Hi again,
i checked both programs. They do _not_ depend on the netpbm tools or the
pbm library.
I can now recompile them on Cygwin with just adding the headers from the
actual netbpm 9.8 distribution.
So we could check in the header files within src/include.
I changed a call to png_write_destroy(), this function is deprecated and
should not be used any more. Perhaps this was another reason for core
dumps.
But i found that the files written by r.out.png are _very_ big
(r.out.png edges from the global dataset yields a file 29 MB big).
Although the image consists only of white and blue pixels. This is IMHO
not compressed at all (4500x2250x8bit x rgb ~ 29 MB). gzipped it shrinks
down to less than 200k.
Any comments?
cu,
Andreas
--
Andreas Lange, 65187 Wiesbaden, Germany, Tel. +49 611 807850
Andreas.Lange@Rhein-Main.de - A.C.Lange@GMX.net
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On Tue, Nov 21, 2000 at 11:44:01PM +0100, Andreas Lange wrote:
Hi again,
i checked both programs. They do _not_ depend on the netpbm tools or the
pbm library.
I can now recompile them on Cygwin with just adding the headers from the
actual netbpm 9.8 distribution.
So we could check in the header files within src/include.
I changed a call to png_write_destroy(), this function is deprecated and
should not be used any more. Perhaps this was another reason for core
dumps.
But i found that the files written by r.out.png are _very_ big
(r.out.png edges from the global dataset yields a file 29 MB big).
Although the image consists only of white and blue pixels. This is IMHO
not compressed at all (4500x2250x8bit x rgb ~ 29 MB). gzipped it shrinks
down to less than 200k.
Haven't looked myself, but does the code specify a compression level
and/or bit packing for the png_lib? Deflate compression (zlib) should
be built in and only needs to be specified at the beginning with a call
like:
png_set_compression_level (png_ptr, Z_DEFAULT_COMPRESSION);
I just gleaned this from the libpng.txt file that came with the library
(I'd hardly claim to be an expert).
I'll be adding zlib.h/libz checks to the configure script and it will
define HAVE_ZLIB_H in src/include/config.h. Actually, I already did
this and then found how the configure script has things *not* in
configure.in (Oooh, bad). Ahh, I see zlib.h is already included in png.h.
Still, configure should check.
--
Eric G. Miller <egm2@jps.net>
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Hi Eric,
thanks for the hint. I'll look into that another time and update the
code of r.in.png and r.out.png.
The pnm.h header includes internally half a dozen other header files,
and in one older version one header that is incompatible with some
Cygwin header.
But i can compile r.in.png and r.out.png now on Linux, IRIX and
Cygnus/Win32.
As a side note: GDAL supports non-georeferenced image formats (jpeg,
png) too, so that i think we should standardize on GDAL in the long
term. The complicated part with image import is IMHO not reading/writing
the image, but the color support for GRASS. And that is not appropriate
with r.in.png/r.out.png.
cu,
Andreas
Eric G . Miller wrote:
Haven't looked myself, but does the code specify a compression level
and/or bit packing for the png_lib? Deflate compression (zlib) should
be built in and only needs to be specified at the beginning with a call
like:
png_set_compression_level (png_ptr, Z_DEFAULT_COMPRESSION);
I just gleaned this from the libpng.txt file that came with the library
(I'd hardly claim to be an expert).
I'll be adding zlib.h/libz checks to the configure script and it will
define HAVE_ZLIB_H in src/include/config.h. Actually, I already did
this and then found how the configure script has things *not* in
configure.in (Oooh, bad). Ahh, I see zlib.h is already included in png.h.
Still, configure should check.
--
Eric G. Miller <egm2@jps.net>
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--
Andreas Lange, 65187 Wiesbaden, Germany, Tel. +49 611 807850
Andreas.Lange@Rhein-Main.de - A.C.Lange@GMX.net
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