RRLuminanceFromRGBComponents.m #1

// RRUtils RRLuminanceFromRGBComponents.m
//
// Copyright © 2008, Roy Ratcliffe, Lancaster, United Kingdom
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//
//------------------------------------------------------------------------------

#import "RRLuminanceFromRGBComponents.h"

// http://www.opengl.org/resources/code/samples/advanced/advanced97/notes/node140.html
CGFloat RRLuminanceFromRGBComponents(const CGFloat *rgb)
{
	// 0.3086 + 0.6094 + 0.0820 = 1.0
	return 0.3086f*rgb[0] + 0.6094f*rgb[1] + 0.0820f*rgb[2];
}