Message-ID: 39E8DAF4.C6B79719@home.com
To: TIFF Mailing List <tiff@olympiakos.com>
Subject: tif_getimage.c and YCbCr
From: Frank Warmerdam <warmerda@home.com>
Date: Sat, 14 Oct 2000 17:15:16 -0500
Sender: owner-tiff@olympiakos.com


Folks, 

There seem to be some serious bugs in the YCbCr support in tif_getimage.c
(the ReadRGBAImage code) for odd sized images.  For instance it doesn't
work properly for 4,4 sampled code unless the image width and height is
a multiple of four (and strip or tiles sizes are also a multiple of four). 

Before I spend alot of time trying to fix this I would ask:

 o Is there anything in the specification that requires factorable sizes when
   using YCbCr images?

 o Is there anyone else interested in fixing this problem?  Ideally someone
   who cares more about YCbCr images than I, and who can do more testing than
   I might?  

 o Any other advice?

The bugs can be reproduced by converting an odd sized image to YCbCr form
with "rgb2ycbcr -h 4 -v 4 -c none", and then trying to convert back to 
RGBA with tiff2rgba. 

Best regards,

---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerda@home.com
light and sound - activate the windows | http://members.home.com/warmerda
and watch the world go round - Rush    | Geospatial Programmer for Rent

