0

Does anyone know where I can find good documentation on the CITT4 algorithm? Something I can use to implement my own decoder? I'm working with an ancient set of TIFF data that's encoded with CCITT4 and only Adobe photoshop is able to open some of the files.

I thought that maybe if I were to write my own decoder I might be able to figure out why. My goal ultimately is to be able to use open source tools like ImageMagick to convert all my data to PDF. We're talking thousands and thousands of files here so I need to engineer a robust and automated solution.

Here's the best I've found so far online. I'm an engineer and at a very high level, understand the rudiments of huffman encoding, compression algorithms and alphabets. There just doesn't seem to be enough documentation online for me to write a proper piece of spec-compliant software. I'm even willing to purchase a book if someone has a good recommendation.

Here's a related question I posted earlier with more background to what I'm doing.

Andrew
  • 421
  • 2
  • 12
  • Are you asking for somebody to read the spec and write the code for you? Or to explain Huffman coding? The latter is no problem but the former is potentially too open-ended to get a good answer here. – Patrick87 Nov 07 '17 at 18:08
  • @Patrick87 I'm not asking anyone to write code for me. I'm just looking for a bit more detail on CCITT4 I guess. I took information theory nearly 25 years ago. The spec document was a bit hard to digest I guess and so i was wondering if there was something a bit more verbose out there. If not I'll slog through it. – Andrew Nov 07 '17 at 22:54
  • 1
    I'm not ready to make my G4 codec public, but I would suggest you make use of the libtiff source code. You can link it to your project and run the decoder in a debugger to see exactly how it works. I think you'll find that it's able to open all of your files. – BitBank Nov 08 '17 at 00:08
  • @BitBank. Thanks for the excellent suggestion. I'll see what mileage I can get out of it. – Andrew Nov 08 '17 at 00:21
  • If you're still having trouble and you don't think the questions are appropriate for SO, you can email me - bitbank@pobox.com – BitBank Nov 11 '17 at 14:39

0 Answers0