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May 2005
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2005.05.30 09:58 "Re: how to convert a JPEG-IN-TIFF file to jpeg file without decomress & compress", by Kelvin Zhong
Thanks,Joris, now i can convert a JPEG-IN-TIFF file to jpeg file without decomress & compress under the assumption:JPEG-IN-TIFF was writed as a single strip. but i would like to enhance this function more... cause i saw some description below in the TIFF Tech-Notes 2: page 12 of 15: It is possible to convert an interchange-JPEG file (e.g., a JFIF file) to TIFF simply by dropping the interchange datastream into a single strip.(However, designers are reminded that the TIFF spec discourages huge strips; splitting the image is somewhat more work but may give better results.) Conversion from TIFF to interchange JPEG is more complex. A strip-based TIFF/JPEG file can be converted fairly easily if all strips use identical JPEG tables and no RSTn markers: just delete the overhead markers and insert RSTn markers between strips. Converting tiled images is harder,since the data will usually not be in the right order (unless the tiles are only one MCU high). This can still be done losslessly, but it will require undoing and redoing the entropy coding so that the DC oefficient differences can be updated. It seems multiple-strips also can do such things like single-strip.(JPEG-IN-TIFF files). and i try to do like this, but it need another marker : called DRI ? I was puzzled how(where) to get the DRI value ? in the tif file ? do anyone know something about this ? any kind of information that related to this problem is ok. thanks . yourpattern@126.com Kelvin.zhong