How to calculate the luminance of an image?

1. How is luminance value calculated?
2. How is luminance color calculated?
3. What is image luminance?

How is luminance value calculated?

Alternatively, the luminance of a surface can be calculated from the formula L = E x § / ¹ where § is the luminance factor of the surface material and is read from a table of values. If the surface is diffuse then § can be replaced with "p", the diffuse reflection coefficient for the material.

How is luminance color calculated?

Definition as Stated in WCAG 2.

Note 1: For the sRGB colorspace, the relative luminance of a color is defined as L = 0.2126 * R + 0.7152 * G + 0.0722 * B where R, G and B are defined as: if RsRGB <= 0.03928 then R = RsRGB/12.92 else R = ((RsRGB+0.055)/1.055) ^ 2.4.

What is image luminance?

Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls within a given solid angle.