Grayscale Image

Each color pixel in an image is typically defined by a triplet of red, green, and blue (RGB) values. But it is also possible to define it by a HSV triplet for hue (rather red, rather green, rather blue), saturation (rather bright color or rather grayish) and luminosity/value (rather light or rather dark). This brightness value is generally used to define the position / color of the pixel between black and white and thus obtain a grayscale image.

To calculate this luminosity, several algorithms / color referentials are possible, such as recommendations 709, 601 or 2100 used as a standard in photography or video (and from the CIE Commission Internationale de l'Éclairage).

dCode calculates the brightness value for each pixel in the image and returns a gray pixel of corresponding brightness.

If an error is returned, it may be an altered file, a bad image, or the file format does not match its extension.

A gray scale is the set of shades of gray used in an image. The number of shades of gray is used to define the size of the scale.

By default, the gray scales are 256 levels of gray.

Recommendation 709 is used as a standard for HDTV. The luminance is calculated as Gray = 0.2125 * Red + 0.7154 * Green + 0.0721 * Blue

Example: A color representing the color Orange consisting of Red = 255, Green = 127, Blue = 0. Then the value of gray is 255*0.2125+127*0.7154+0*0.0721=145

Recommendation 601 was used as a standard for analogic terrestrial television. Luminance is calculated as Gray = 0.299 * Red + 0.587 * Green + 0.114 * Blue

Example: A color representing the color Orange consisting of Red = 255, Green = 127, Blue = 0. Then the value of gray is 255*0.299+127*0.587+0*0.0114=151