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December 1999
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1999.12.07 09:06 "Re: ZIP/Deflate", by Ivo Penzar
Last week I asked (following the saga on Adobe, Rev. 7, LZW and ZIP), which value (tag=259, compression) Adobe's new Photoshop and ImageReady use for their support of ZIP/Deflate compression scheme. I.e., what do they use instead of the private value COMPRESSION_DEFLATE=32946, as defined in libtiff's tiff.h. Supposedly, this new value is also to be officially expected for the upcoming TIFF Rev. 7, once Adobe decides to publish it. In the meantime, it was easy to find this answer myself. Both Photoshop 5.5 and ImageReady 2.0 support only reading of ZIP/Deflate compressed TIFF images, and to define it they expect value=8 (tag=259). I.e., 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. 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. Now I have to more questions to go: 1) Apparently, Corel's Draw and Photo Paint read and write WI images (Wavelet compressed format). Interestingly, WI images created by Draw or Photo Paint, WEB Photo Paint (claimed to be built on the same technology) refuses to open, explaining that these are corrupt WI files. As expected, this lossy compression provides much better results than JPEG. Unfortunately, both Draw and Photo Paint refuse to write WI images larger than 2048x2048, although I don't see a mathematical grounding for these highly artificial restrictions (except for probably an inappropriate design of WI format itself). Does anybody know where can I find the precise specification for that WI format (not the theory of wavelet compression itself). Also, do you know of any other imaging tool to support the WI raster image files. 2) Except for ImageMagick and similar open-source products, I didn't find a widely used commercial product (at least those ubiquitous by Corel and Adobe) to support JBIG format. What is actually the past, present and future of the JBIG format and what are its main characteristics? As far as I understand (I didn't look into the open-sourced libjbig code), JBIG is by definition restricted to bilevel images, and uses some sort of arithmetic coding compression (as patented by IBM). Ivo