LibTiff Mailing List

I'm working to 12 bits jpegs in tiff files.
For now, for jpeglib side, most is done, for runtime selection
of 12 bits or 8 bits data ( in one or two bytes samples ).
In libtiff, all that is processed by Decode/Encode ( not raw )
is ok : 8 bits, 12 bits packed, and 16 bits. 
Yes 16 bits Jpeg, a 16 bits jpeg compression begin 
by a bandwitdh reduction to 12 bits, everybody know that ... :-)

Work with most of the tools coming with libtiff.
So linked with ImageMagik for sample, loading 12/8 bits jpegs,
8/16 bits tiffs. Not 12 at this time, cause Readrgba to make aware.

Problems come with DecodeRaw/EncodeRaw process.
This concern in turn, case ContigDownsampled <--> ContigDownsampled
compress/decompress. Thing independant of data precision and is the same 
for native libs 8 bits.
TiffScanlineSize do not take account of downsamplings 
for contig downsampled YCC. I don't find in specs or docs 
if this is "by definition" or buggy.

This cause a lot of problems in the "raw" scheme. 
"bytesperline" member do not match the real count byte 
input/output to/from jpegcodec, and cause "too much, too few,
fractionnal ... scanlines" errors.

Have made a correction, limited to tiffjpeg ( if in tif_strip ... ;-((( ), 
and intensively test the things with rgbtoycbcr, tiffcp, tiff2rgba,
---> files 571x379, stripped or not, with downsamplings 2 2, 1 2, 2 1,
jpeg compressed or not.
Except 2 1 ( tiffrgba don't want ) all files are correct and well
displayed by imagemagick, the gimp, psp. Photoshop want only jpegs.

The question about scanlinesize, is because I need to be sure of the
exact meaning of returned value, before doing some job for 12 bits
support.

Another point, is about "tif->tif_row" member. For stripped files,
it's value is relative to the beginning of the strip, not the file.
Is this correct ?

--
Jean-Yves


AWARE [SYSTEMS]		Imaging expertise for the Delphi developer
		TIFF and LibTiff Mailing List Archive
	LibTiff Mailing List TIFF and LibTiff Mailing List Archive May 2005 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	2005.05.05 19:26 "TiffScanlineSize", by Jean Yves Le Ridant I'm working to 12 bits jpegs in tiff files. For now, for jpeglib side, most is done, for runtime selection of 12 bits or 8 bits data ( in one or two bytes samples ). In libtiff, all that is processed by Decode/Encode ( not raw ) is ok : 8 bits, 12 bits packed, and 16 bits. Yes 16 bits Jpeg, a 16 bits jpeg compression begin by a bandwitdh reduction to 12 bits, everybody know that ... :-) Work with most of the tools coming with libtiff. So linked with ImageMagik for sample, loading 12/8 bits jpegs, 8/16 bits tiffs. Not 12 at this time, cause Readrgba to make aware. Problems come with DecodeRaw/EncodeRaw process. This concern in turn, case ContigDownsampled <--> ContigDownsampled compress/decompress. Thing independant of data precision and is the same for native libs 8 bits. TiffScanlineSize do not take account of downsamplings for contig downsampled YCC. I don't find in specs or docs if this is "by definition" or buggy. This cause a lot of problems in the "raw" scheme. "bytesperline" member do not match the real count byte input/output to/from jpegcodec, and cause "too much, too few, fractionnal ... scanlines" errors. Have made a correction, limited to tiffjpeg ( if in tif_strip ... ;-((( ), and intensively test the things with rgbtoycbcr, tiffcp, tiff2rgba, ---> files 571x379, stripped or not, with downsamplings 2 2, 1 2, 2 1, jpeg compressed or not. Except 2 1 ( tiffrgba don't want ) all files are correct and well displayed by imagemagick, the gimp, psp. Photoshop want only jpegs. The question about scanlinesize, is because I need to be sure of the exact meaning of returned value, before doing some job for 12 bits support. Another point, is about "tif->tif_row" member. For stripped files, it's value is relative to the beginning of the strip, not the file. Is this correct ? -- Jean-Yves

LibTiff Mailing List

2005.05.05 19:26 "TiffScanlineSize", by Jean Yves Le Ridant