How to measure the contrast between any given color and white?

1. How do you measure contrast between colors?
2. How do you measure contrast?
3. How do you measure contrast in an image?
4. What is the contrast ratio of black and white?

How do you measure contrast between colors?

Calculating a Contrast Ratio

Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1). (L1 + 0.05) / (L2 + 0.05), whereby: L1 is the relative luminance of the lighter of the colors, and. L2 is the relative luminance of the darker of the colors.

How do you measure contrast?

Contrast is calculated using "relative luminance", which is defined as: The relative brightness of any point in a colorspace, normalized to 0 for darkest black and 1 for lightest white. The relative luminance can be calculated from any colour code (like HEX or RGB).

How do you measure contrast in an image?

Contrast is defined as the difference between the highest and lowest intensity value of the image. So you can easily calculate it from the respective histogram. Example: If you have a plain white image, the lowest and highest value are both 255, thus the contrast is 255-255=0.

What is the contrast ratio of black and white?

WCAG 2 "Contrast Ratio"

This brightness difference is expressed as a ratio ranging from 1:1 (e.g. white on white) to 21:1 (e.g., black on a white). To give a frame of reference, on a white background: Pure red (#FF0000) has a ratio of 4:1.