Update graphicsmagick with quantum depth = 16

[Marco Atzeri <marco_atzeri at yahoo dot it>]

Dear users,
I am thinking to update GraphicsMagick-1.3.12
moving from "quantum depth = 8" to "quantum depth = 16"

following a discussion on octave bug list
http://savannah.gnu.org/bugs/?30715
about the improved image quality using the higher quantum depth,
specially for medical and scientific images.

For details about the difference
http://www.graphicsmagick.org/INSTALL-unix.html
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Larger pixel quantums cause GraphicsMagick to run more slowly and to require more memory. For example, using sixteen-bit pixel quantums causes GraphicsMagick to run 15% to 50% slower (and take twice as much memory) than when it is built to support eight-bit pixel quantums.

The amount of virtual memory consumed by an image can be computed by the equation (QuantumDepth*Rows*Columns*5)/8. This is an important consideration when resources are limited, particularly since processing an image may require several images to be in memory at one time. The following table shows memory consumption values for a 1024x768 image:

    QuantumDepth 	Virtual Memory
    8 	                3MB
    16 	                8MB
    32 	                15MB

GraphicsMagick performs all image processing computations using double-precision floating point so results are very accurate. Increasing the quantum storage size decreases the amount of quantization noise (usually not visible at 8 bits) and helps prevent countouring and posterization in the image.
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Anyone having problem with it ?
Of course I will update octave to use this improvement.

Regards
Marco Atzeri 





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