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[Octave-bug-tracker] [bug #39249] imread and 32 bit (float) TIFF images


From: Patrick Noffke
Subject: [Octave-bug-tracker] [bug #39249] imread and 32 bit (float) TIFF images
Date: Fri, 18 Oct 2013 16:12:14 +0000
User-agent: Opera/9.80 (X11; Linux x86_64) Presto/2.12.388 Version/12.16

Follow-up Comment #9, bug #39249 (project octave):

I don't think GM's behavior of scaling the image is correct.  The min/max
sample value are not required tags, and if they are set, they do not mean the
image cannot have pixel values outside the corrsponding range.

>From the TIFF specification about MaxSampleValue:

"This field is not to be used to affect the visual appearance of an image when
it is
displayed or printed. Nor should this field affect the interpretation of any
other
field; it is used only for statistical purposes.

Default is 2**(BitsPerSample) - 1."

If an image is floating point, Octave should return an array of the
single-precision floating point values unmodified.  This is how Matlab
behaves.

I'm not sure if GM can be modified to work this way, or if we need to handle
loading floating-point TIFFs specially (i.e. use libtiff directly).

Either way, I don't think the bug should be closed.  I would like to work on
this at some point.

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  <http://savannah.gnu.org/bugs/?39249>

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