2008.10.23 20:12 "Re: [Tiff] JPEGSetupEncode messages", by Bob Friesenhahn
Is there any way of telling at runtime from the command line (or with perlmagick) whether libjpeg is compiled for 8 or 12 bit? Or can I safely assume that it is 8 bit?
12 bit JPEG is very rare. I don't know of a way to ask libtiff what JPEG depth it supports. If you include the libjpeg headers, then the define BITS_IN_JSAMPLE will be '12' if the associated libjpeg is compiled for 12 bits. However, it is theoretically possible that libtiff was not compiled against that header or library.
Unless you are planning on making the huge effort required to support 8/12 bit JPEG in the same application (or finish the work on David Gabriel's bi-modal libjpeg) I would not worry about 12 bit JPEG.
I think that 12 bit JPEG is a very good thing but since libjpeg makes it difficult to use, and 12-bit JPEG is quite rarely used, it is best left for specialized applications.
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/