[Octave-bug-tracker] [bug #49653] Build failure with ImageMagick

[Markus Mützel]

Follow-up Comment #15, bug #49653 (project octave):

IIUC, Magick::Quantum is supposed to be an integer type:
http://www.graphicsmagick.org/Magick++/Color.html
https://www.imagemagick.org/Magick++/Quantum.html

It might make sense to explicitly cast the floating point arguments to
(Magick::Quantum) in __magick_read__.cc. It's strange though that it seems
like the compiler implicitly casts to the correct type when compiling with
GraphicksMagick. But it doesn't look like this is happening when you are
compiling with ImageMagick...
Maybe your ImageMagick library was compiled with a quantum depth of 16 and
GraphicsMagick with 8? The compiler might shy from the implicit cast because
the mantissa of a float value isn't large enough for the target integer type?

However, I cannot find anywhere in our code where we call Magick::Color with
float arguments. Unless I'm missing something, we seem to call it with double
arguments everywhere...

Anyway, an explicit cast to the integer type would maybe also make it clearer
to a programmer what is going on in that part of the code.


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