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Date: Thu, 29 Apr 1999 22:57:59 -0700
To: tiff@olympiakos.com
From: Mike Schienle <mgs@ivsoftware.com>
Subject: YCbCr reader help
Sender: owner-tiff@olympiakos.com

Hi all -

I just joined the list so I don't know if there are archives 
available. If so, could someone point them out?

I'm working on a function to read in a TIFF-based YCbCr file and 
return a raw RGB image using a cross-platform language called IDL. 
I'm thoroughly confused at the moment on how to weave through the Y, 
Cb and Cr data elements and place them in arrays before converting 
them to RGB. My source data is in EXIF format with no compression. 
I'm not too concerned with the EXIF headers at the moment. I have the 
TIFF 6.0 spec and the Jeida EXIF spec.

Here's some info about the file:
PlanarConfig = 1
Compression = 1
Width = 1280
Length = 1000
Subsampling = 2, 2
Position = 2
StripsPerImage = 50
RowsPerStrip = 20
StripByteCount = 51200 for all 50 elements of array
StripOffsets = 11234, 62434, 113634, 164834, 216034, etc. (51200 increment)

I've set up a 1280x1000 array for each Y, Cb and Cr section. I expect 
to see the Y array filled, and 1/4 of the Cb and Cr arrays filled, 
which will then be enlarged to the size of the Y array. Is that 
correct? I'm pretty confident I have the transformation equations 
right after I get the data read in correctly.

I'd certainly appreciate any hints on straightening myself out.

Mike Schienle                                 Interactive Visuals, Inc.
mgs@ivsoftware.com                  Remote Sensing and Image Processing
http://www.ivsoftware.com/         Analysis and Application Development
