Edit

[EDIT] FILE: sGray

% Copyright (C) 2001-2019 Artifex Software, Inc.
% All Rights Reserved.
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% This software is provided AS-IS with no warranty, either express or
% implied.
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% This software is distributed under license and may not be copied,
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% of the license contained in the file LICENSE in this distribution.
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% Artifex Software, Inc.,  1305 Grant Avenue - Suite 200, Novato,
% CA 94945, U.S.A., +1(415)492-9861, for further information.
%

% One-component color space similar to sRGB color space.

currentglobal true setglobal

/sGray
[ /CIEBasedA
  3 dict begin
    /WhitePoint [ 0.9505 1 1.0890 ] def % D65

/DecodeLMN [  % sRGB gamma transform 
      { dup 0.03928 le { 12.92321 div } { 0.055 add 1.055 div 2.4 exp } ifelse }
      bind dup dup ] def

/MatrixLMN [ % sRGB to XYZ (D65) matrix (ITU-R BT.709-2 Primaries)
      0.412457 0.212673 0.019334
      0.357576 0.715152 0.119192
      0.180437 0.072175 0.950301 ] def
  currentdict end
] 
/ColorSpace defineresource pop

setglobal

CANCEL