2001.03.21 17:33 "Re: Wang tiff", by Neil Durant

I looked at the sample file. This is a single-page Wang TIFF, which means that it can be treated as a TIFF file with an unknown tag. Wang private tag, 0x80a6, contains an offset to the page control structure. In your file, this value is 0, which means the page contains a single page only. I should note, though, that the Wang files I've seen so far use 0x80a7 tag, so I am conjecturing a bit.

I think the problem you face is not Wang format, but rather your JPEG compression. The file uses the old-style compression 6 (JPEG). And uses it with vengeance - the Huffman and quantization tables are scattered throughout, and each block row is compressed in a separate strip. It's well known that this type of compression is ill-defined and should not be used, which is why you are having trouble finding the readers for your file.

Assuming all your files have the same format, you might use the data in your file to reassemble a proper JFIF file without actually decompressing your bitmap.

Hmmm. From what everyone is saying it looks like I'm going to have to do a bit of a reverse-engineering job, and cut the file up and reassemble it.

Does anyone have any URLs etc for where I can find some specifications on the TIFF file format, and how extensions such as these Wang ones are integrated into the format?

Thanks for your help!

Neil

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Neil Durant
<neil@sphere3.demon.co.uk>                        Fax: 08700 520159
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