1999.12.07 14:53 "Re Deflate - Patch for libtiff", by Ivo Penzar

Today I wrote:

Redefine the COMPRESSION_DEFLATE from 32946 to 8 and use the tiffcp tool (for example) to save the TIFF image with ZIP/Deflate compression, and both Photoshop and ImageReady will quietly open this TIFF image just like any other regular TIFF file.

There is a better way, a patch for the libtiff to support BOTH the old value=32946 and the new value=8:

1) In the file tiff.h find the following line (beginning of TIFF Tag Definitions):

#define     COMPRESSION_DEFLATE  32946 /* Deflate compression */

and add a new one right after this:

#define     COMPRESSION_ADOBE_DEFLATE  8 /* Deflate compression, as recognized by Adobe */

2) In the file tif_codec.c find the following line (definition of TIFFCodec _TIFFBuiltinCODECS[] variable)

{ "Deflate", COMPRESSION_DEFLATE, TIFFInitZIP },

and add a new one right after this:

{ "AdobeDeflate", COMPRESSION_ADOBE_DEFLATE, TIFFInitZIP },

3) In the file tif_zip.c find the following line (implementation of TIFFInitZIP() method)

assert(scheme == COMPRESSION_DEFLATE);

and replace it with the following one:

assert((scheme == COMPRESSION_DEFLATE) || (scheme == COMPRESSION_ADOBE_DEFLATE));

That's it!

Otherwise, use ACDC (for example) to convert the TIFF image to the ZIP/Deflate compression, open that file by your favorite HEX editor (mine is A.X.E.), and find the raw byte sequence of 0x010300030000000180b2 (MM), or 0x0301030001000000b280 (II) and change it to 0x01030003000000010008 or 0x03010300010000000800 respectively; the image is ready again to be quietly opened by Photoshop 5.5 or ImageReady 2.0.

Explanation: find and replace tag 259, value=32946 to value=8. I opted to search for all 10 bytes (the whole signature of compression tag) to avoid possible other instances of two-bytes sequence 0x80b2 (MM), i.e., 0xb208 (II).

Ivo