calculateRelativeLuminance
Calculates relative luminance per WCAG 2.0 specification Uses sRGB colorspace with proper gamma correction
Formula: L = 0.2126 * R + 0.7152 * G + 0.0722 * B Where R, G, B are gamma-corrected values
Return
Luminance value between 0.0 (darkest) and 1.0 (lightest)
Parameters
color
The Android Color int value