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Well, I finally made my way to the LibTIFF CVS, and I was happy to find a 
new file, tif_jbig.c.  I couldn't wait to take it home and take it out for a 
spin, so to say, and in no time at all, I was reading and writing TIFF 
JBIG's.

While I applaud the work that Lee Howard has done in bringing JBIG to 
LibTIFF, there are some major limitations with tif_jbig.c:

1. Images can contain only one strip.
2. Tiles are not supported.
3. It appears that only one bit plane is supported.

The first 2 limitations don't bother me, they are relatively easy upgrades.  
I'm more concerned that there might not be enough general interest for 
anyone, myself included, to work on incorporating JBIG with multiple bit 
planes.

I realize that JBIG, by definition, deals with bi-level images and is mostly 
used for faxes, but JBIG's with multiple bit planes can be easily 
constructed, allowing grayscale and color images to be compressed.  The code 
for reading and writing multiple plane JBIG's is nicely illustrated in the 
files jbgtopbm.c and pbmtojbg.c, which are included in Markus Kuhn's 
JBIG-KIT library.

Of course, the problem with stand-alone, multi-plane JBIG files has always 
been that there is no standardized way to encode information such as the 
meaning of the various bit planes, causing the compression of color images 
to be plagued with ambiguity.  However, this ambiguity disappears when we 
incorporate JBIG into TIFF, thanks to basic tags such as photometric 
interpretation, bits per sample, and samples per pixel.  In a manner of 
speaking, multi-plane JBIG compression finds a happy home inside TIFF files.

One might envision a scheme where every strip or tile of a grayscale or 
color image is a n-plane JBIG image, where n is the number of bits per pixel 
(PLANARCONFIG_CONTIG) or n is the number of bits per sample 
(PLANARCONFIG_SEPARATE).

Charles
--------------------------------------------------------

On a different subject now, I was also eager to try out the completely 
rewritten tif_ojpeg.c file.  It's a masterpiece, although I did think that 
the warning handler message was a little wordy.  My entire collection of 
OJPEG images displayed beautifully, even the grayscale and multipage ones.  
Joris is certainly a genius, but I guess we all have suspected that for 
quite some time.  I really enjoyed finally being able to see Zack the Cat 
with crystal clarity.  I wonder if old Zack has passed away since that 
picture was taken?


AWARE [SYSTEMS]		Imaging expertise for the Delphi developer
		TIFF and LibTiff Mailing List Archive
	LibTiff Mailing List TIFF and LibTiff Mailing List Archive June 2006 Previous Thread Next Thread Previous by Thread Next by Thread Previous by Date Next by Date Contact The TIFF Mailing List Homepage This list is run by Frank Warmerdam Archive maintained by AWare Systems	Thread 2006.06.23 04:45 "TIFF JBIG", by Charles Auer 2006.06.23 09:52 "Re: TIFF JBIG", by Joris Van Damme 2006.06.23 15:38 "Re: TIFF JBIG", by Charles Auer 2006.06.23 04:45 "TIFF JBIG", by Charles Auer Well, I finally made my way to the LibTIFF CVS, and I was happy to find a new file, tif_jbig.c. I couldn't wait to take it home and take it out for a spin, so to say, and in no time at all, I was reading and writing TIFF JBIG's. While I applaud the work that Lee Howard has done in bringing JBIG to LibTIFF, there are some major limitations with tif_jbig.c: 1. Images can contain only one strip. 2. Tiles are not supported. 3. It appears that only one bit plane is supported. The first 2 limitations don't bother me, they are relatively easy upgrades. I'm more concerned that there might not be enough general interest for anyone, myself included, to work on incorporating JBIG with multiple bit planes. I realize that JBIG, by definition, deals with bi-level images and is mostly used for faxes, but JBIG's with multiple bit planes can be easily constructed, allowing grayscale and color images to be compressed. The code for reading and writing multiple plane JBIG's is nicely illustrated in the files jbgtopbm.c and pbmtojbg.c, which are included in Markus Kuhn's JBIG-KIT library. Of course, the problem with stand-alone, multi-plane JBIG files has always been that there is no standardized way to encode information such as the meaning of the various bit planes, causing the compression of color images to be plagued with ambiguity. However, this ambiguity disappears when we incorporate JBIG into TIFF, thanks to basic tags such as photometric interpretation, bits per sample, and samples per pixel. In a manner of speaking, multi-plane JBIG compression finds a happy home inside TIFF files. One might envision a scheme where every strip or tile of a grayscale or color image is a n-plane JBIG image, where n is the number of bits per pixel (PLANARCONFIG_CONTIG) or n is the number of bits per sample (PLANARCONFIG_SEPARATE). Charles -------------------------------------------------------- On a different subject now, I was also eager to try out the completely rewritten tif_ojpeg.c file. It's a masterpiece, although I did think that the warning handler message was a little wordy. My entire collection of OJPEG images displayed beautifully, even the grayscale and multipage ones. Joris is certainly a genius, but I guess we all have suspected that for quite some time. I really enjoyed finally being able to see Zack the Cat with crystal clarity. I wonder if old Zack has passed away since that picture was taken?

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2006.06.23 04:45 "TIFF JBIG", by Charles Auer