1999.04.30 05:57 "YCbCr reader help", by Mike Schienle

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