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[Octave-bug-tracker] [bug #30715] imread fails to read uint16 tif image

From: Jonathan Thomson
Subject: [Octave-bug-tracker] [bug #30715] imread fails to read uint16 tif image
Date: Fri, 03 Sep 2010 03:38:50 +0000
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-us) AppleWebKit/531.2+ (KHTML, like Gecko) Safari/531.2+ Debian/squeeze (2.30.2-3) Epiphany/2.30.2

Follow-up Comment #12, bug #30715 (project octave):

This is from an email from Bob Friesenhahn, GraphicsMagick Maintainer.

[begin e-mail]
> Is there any way at all, in GraphicsMagick, to determine that the precision
of an image has been down-scaled?

Not that I am aware of.  With over 100 subformats, accomplishing that could
be challenging.  With quite a lot of effort, additional attributes could be
added to the image which provide more origin information.  It is not always
possible to know the actual depth.
Useful attributes could be added for just a few important subformats.

The easiest solution is to always use the Q16 build.  This does take more
memory and is slower, but it is also the build that I spend most of my time
optimizing.  There is also a Q32 build for fanatics.

Even with the Q16 or Q32 build there are some formats which will still lose
information, such as formats containing 32 or 64 bit floats.

[end e-mail]

I believe the QuantumDepth limitation stems from the fact that GraphicsMagick
is not just an image reader but is an integer math image manipulation program.
Perhaps there is some other library (better suited for Octave) that's purpose
is to simply read and write image data without loss of precision.


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