1995.01.24 18:33 "Re: TIFF YCbCr", by Sam Leffler

I'm devolloping a DOS based application that handles TIFF files. Actually I have two items on my TO DO list:

• Read TIFF FAX G4 compression
• Write TIFF YCbCr files.

I've been implementing the TIFF G3 reader using tries for about a year. I've both the CCITT standard and a recent beta of Sam Leffler TIFF library, but I still have to understand it. Any hint welcome.

There are working G3 and G4 codecs in the library; they've been there for many years.

It seems to me the TIFF library doesn't support YCbCr. If I'm right, Is the use of YCbCr disrecommanded or (the usual thing) am I just overlooking some files in TIFF library.

There has been "support" for YCbCr data for quite a long time. v3.3beta021 is the current distribution.

I could make good use of a set of test TIFF files: planar and packed YCbCr files, Palette files with extra samples, TIFF files with more than 8 bits/pixel, even some CIE Lab files. I would like to be sure my viewer aborts gracefully as recommended. If anyone know where to get those, I'll be gratefull if he could let me know.

Palette files are explicitly intended for RGB or greyscale data; not YCbCr. There is no direct support for CIELab data in the current library. tools/rgb2ycbcr.c is an example program that converts an RGB image to a YCbCr image; you can use/modify it to generate some test files.

    Sam