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2009.03.16 12:36 "Re: Needs help on implementing the JPEG 7 compression", by Gerben Vos
The "#define JPEG_LIB_VERSION 61 /* Version 6a */" indicates the version of the *JPEG* library. The JPEG library can be downloaded separately from http://www.ijg.org/ . The current version of the JPEG library is actually version 6b (and has been since 1999). In fact, I'm surprised that you find a file called "jpeglib.h" in libtiff. It's not supposed to be there; it's part of libjpeg. Please don't confuse the two. The *TIFF* compression type numbers (of which 6 and 7 indicate a type of JPEG compression) have nothing at all to do with the version number of the JPEG library. In fact, the JPEG compression used by TIFF compression types 6 and 7 is the same. These TIFF compression types are just different ways of encapsulating the JPEG-compressed data within the TIFF format. I have also posted this answer to the mailing list. Please stay on the mailing list with further questions, as long as they remain TIFF-related. Gerben. -----Original Message----- From: Sanjeev Balachander [mailto:sanjeevb@vitinfotech.com] Sent: Monday, 16 March, 2009 13:03 To: Gerben Vos Subject: Re: [Tiff] Needs help on implementing the JPEG 7 compression - [[SPF]] Sender is forged (SPF Fail) Hi Gerben, Thanks for your response. Indeed i looked into the libtiff as suggested by you. However just have a question from you on correct version. In the tif_jpeg.c it is including a file called Jpeglib.h. In that file there is some thing like this #define JPEG_LIB_VERSION 61 /* Version 6a */ in line 35. What actually is this ? Is this is library version ? How to make sure that this is using compression 7. Thanks Sanjeev Balachander ----- Original Message ----- From: "Gerben Vos" <Gerben@ZyLAB.COM> To: <Tiff@lists.maptools.org> Sent: Monday, March 16, 2009 4:24 PM Subject: Re: [Tiff] Needs help on implementing the JPEG 7 compression > Sanjeev Balachander wrote: > >> I have a requirement where in i had to incorporate the JPEG 7 >> compression. When i searched in the net i am getting an algorithm for >> only JPEG 6 . I am in need of some sample c code for implementin the >> JPEG 7 compression to the TIFF images. If some one is having kindly >> do share the same if possible. > > Interesting! Where did you find the algorithm for compression type 6 > (old-style JPEG-in-TIFF)? > > C code for compression type 7 (new-style JPEG-in-TIFF) has been > available for a long time as part of libtiff. Just download it from > http://www.remotesensing.com/libtiff/ . The code is in tif_jpeg.c . > > A specification of compression type 7 can be found at > http://www.remotesensing.org/libtiff/TIFFTechNote2.html > > This document also explains why it is a terribly bad idea to try to > implement compression type 6. Libtiff contains read-only code for this > deprecated compression type. > > Gerben Vos. > _______________________________________________ > Tiff mailing list: Tiff@lists.maptools.org > http://lists.maptools.org/mailman/listinfo/tiff > http://www.remotesensing.org/libtiff/