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April 2006
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2006.04.10 14:21 "Re: application supplied JPEGTables", by Gerben Vos
yourpattern wrote:
> It's quit useful if the use can specified it's own quantization tables
> for JPEG compression.
> and I would like to propose the addition of the capablity of supporting
> application supplied JPEGTables. this would make the control of image
> quality of JPEG compress more powerful. currently , the only way to
> control the jpeg quality is TIFFSetField(tif, TIFFTAG_JPEGQUALITY,
> nQuality);
> and if we supply a way like :
> TIFFSedField(tif,TIFFTAG_JPEGQUALITYTABLE,nTableType,nTableData,nTableDataSize);
> or something else.
I agree that it would be nice to be able to specify the quantisation tables
using a pseudo tag. I think the only problem will be that you have to be
careful with the TIFFTAG_JPEGTABLESMODE pseudo tag, because it also affects
the quantisation table handling.
However, maybe for your application at this moment it would be easier to do
the JPEG compression yourself, and then use the raw strip/tile writing
functions?
Gerben Vos.