1997.05.01 10:35 "tiled-pyramidal-LAB-JPEG-TIFF", by John Cupitt

Dear TIFF-list,

I've added tiled-pyramidal-LAB-JPEG-TIFF (there should be an acronym for this) to our image processing library and image viewer. It all seems to work fine, thanks very much for all the great free code, but I have a couple of questions:

• I'm not using SubIFD and FILETYPE_REDUCEDIMAGE at the moment, I just have each layer of my pyramid in a top-level TIFF directory, with the biggest first. Does anyone have some simple bit of code I could use as a model for creating SubIFD files? I tried reading thumbnail.c, but something even simpler would be great.
• Does anyone know of a test image which uses this variant of TIFF? I'd like to check I've done it correctly. I can offer a 10k by 10k image of a painting taken directly from the object with a calibrated digital camera free to anyone interested.
• I'm using PHOTOMETRIC_CIELAB, and COMPRESSION_JPEG. Does the JPEG layer know about LAB, ie. does it replace its RGB->YCC conversion with something more appropriate? I'm getting some sightly funny effects ...

All help appreciated, thanks very much,

John Cupitt

--
John Cupitt, john@giorgio.hart.bbk.ac.uk, +44 (0)171 930 2108
VASARI Lab, The National Gallery, Trafalgar Square, London, WC2N 5DN