GraphicsMagick & grayscale

The latest GraphicsMagick 1.2 snapshot supports two grayscale 
colorspaces rather than just one.  GraphicsMagick's RGB to grayscale 
translation has been based on ITU-R 601, which is targeted towards 
legacy television formats which target small screens (e.g. NTSC TV). 
ITU-R 709 provides a new formula which is targeted for HDTV and is 
described to be more accurate for modern CRT monitors and computer 
graphics.

Since there are two standards in use, GraphicsMagick now supports a 
"Rec601Luma" space and a "Rec709Luma" space.  For backwards 
compatibility, GraphicsMagick defaults to the Rec 601 formula.  This 
means that using '-colorspace GRAY' still obtains the Rec 601 results.

In order to specifically select Rec 601 output, use
'-colorspace Rec601Luma' and to select Rec 709 output use
'-colorspace Rec709Luma'.

While the C and C++ APIs have been extended to support the two 
colorspaces, care has been taken to ensure that existing code 
continues to compile and produces the same result.

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


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