func Grayscale() Filter {
	return &colorFilter{
		fn: func(px pixel) pixel {
			y := 0.299*px.r + 0.587*px.g + 0.114*px.b
			return pixel{y, y, y, px.a}
		},
	}
}
// Grayscale creates a filter that produces a grayscale version of an image.
Grayscale creates a filter that produces a grayscale version of an image.
// Grayscale creates a filter that produces a grayscale version of an image .
func Grayscale() Filter {
	return &colorFilter{
		fn: func(px pixel) pixel {
			y := 0.299*px.r + 0.587*px.g + 0.114*px.b
			return pixel{y, y, y, px.a}
		},
	}
}
func Grayscale ( ) Filter { return & colorFilter { fn : func ( px pixel ) pixel { y := 0.299 * px . r + 0.587 * px . g + 0.114 * px . b return pixel { y , y , y , px . a } } , } }
Grayscale creates a filter that produces a grayscale version of an image.
Grayscale creates a filter that produces a grayscale version of an image .