Calculates the contrast ratio between two colors according to WCAG 2.0.
The contrast ratio is defined as (L1 + 0.05) / (L2 + 0.05), where
L1 is the relative luminance of the lighter of the two colors, and
L2 is the relative luminance of the darker of the two colors.
Calculates the contrast ratio between two colors according to WCAG 2.0.
The contrast ratio is defined as (L1 + 0.05) / (L2 + 0.05), where L1 is the relative luminance of the lighter of the two colors, and L2 is the relative luminance of the darker of the two colors.