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October 2005
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This list is run by Frank Warmerdam
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2005.10.26 17:47 "Re: checking test images", by <ryuki_dono@yahoo.de>
Hi Frank! I know that TIFF is a very complex format. In the last months I looked into the descriptions of GIF, JPEG, PNG and TIFF file structure (ok BMP too). My point of view on the topic is how images work with damages. How easy is it to say "That image file is corrupted!"? So I wrote functions (without library support) to check the filestructure, but since math isn't my strong point I use libraryfunctions for decoding the imagedata. You have to see, how much work people put in such libraries. Even if I try to write it myself it would take me to much time and it is realy not easy to find every bug or special case to make it more compatible. The thing with the errormanager... There isn't much help with it in the man pages. I tried to find help with the provided sources of tools. I tried to compare it with jpeg.lib and png.lib that use a similar system. Jpeg.lib uses longjump and a jumpbuffer to jump from the errorhandler function to a block of instruction. Png.lib uses exceptions and/or longjumps in the same manner. Since both keep track of allocated memory and provide "abort and cleanup" functions it is save (?) that way. I only used the png approach with try and catch. Thank you for your notes. I will try and see if I can cleanup my code some more. With best regards