Re: Linear Colorspace

On Wed, 2 Dec 2015, Sam Wilson wrote:

> Hey graphicsmagick-help,
>
> I need your assistance! I'm trying to resize an image
> (http://www.4p8.com/eric.brasseur/gamma_dalai_lama_gray.jpg) using a
> linear colorspace. I can't seem to get GraphicsMagick to actually do the
> conversion. I'm probably making a really dumb mistake, but any input
> would be hugely appreciated. The code below seems to work with
> ImageMagick 6.9.2-7, but not with GraphicsMagick 1.3.23 (obviously
> change MagickCore to MagickLib.)

One thing I see is use of ColorspaceType::sRGBColorspace.  In 
GraphicsMagick this is a special-purpose colorspace just for Kodak 
PhotoCD and not sRGB.  Use ColorspaceType::RGBColorspace instead.

What do you mean by "Linear Colorspace"?  What are you actually trying 
to accomplish?

Sometimes "linear" is used to describe gamma coding, but could be 
"linear light" (no gamma) or "linear intensity" (often 1.2 gamma). 
GraphicsMagick assumes that RGB data is similar to "linear intensity" 
sRGB (or Rec.709) but without using ICC color profiles there is no 
assurance of the actual colorspace.

Bob
-- 
Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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