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April 2007
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2007.04.12 02:13 "Re: O-JPEG problems", by Joris Van Damme
Mick, Mick O'Neill wrote: > I have encountered a number of TIFF files that have images in the > OJPEG format (type 6), but do not contain the JPEGInterchangeFormat > Tag. When this problem was first recognised (about 18 months ago), I > was able to put the following modification into the OJepgSetupDecode > function to allow for it: You've found one of the problems of the old OJPEG decoder, but unfortunately this problem was far from the only one. There were many other types of OJPEG this decoder didn't like, and on some it actually crashed access violation style, so can't actually safely recommend it which is why it was disabled by default. This is why we've replaced it with a totally new one, build from scratch, that is far more robust, and supports very nearly all OJPEG images out there, including many types without JPEGInterchangeFormat tag. We feel more confident with this new OJPEG codec, which is why this one is enabled by default. We did this new OJPEG after the release of the latest stable version, so if you need it you need to get a hold of a CVS copy. In order to do that, see the instructions on LibTiff homepage (http://www.remotesensing.org/libtiff/). Make sure you check out the stable branch-3-9, not CVS head that is a currently unstable BigTIFF upgrade in progress. Unfortunately, we cannot actually do any bug hunting and patching of the previous unstable OJPEG decoder. It would be mission impossible given its inadequate design, and waste of time seeing the new one is there to replace it. I did test your TestBig.tif file with the new OJPEG decoder, though, and all 14 IFDs decode fine. Best regards, Joris Van Damme info@awaresystems.be http://www.awaresystems.be/ Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html