image_rgb_to_gray

image_rgb_to_gray, an Octave code which creates a grayscale version of an RGB image.

An RGB image is an (M,N,3) array.

A grayscale image is an (M,N) array.

A grayscale version of an RGB image can be made by averaging the RGB components of each pixel.

A more sophisticated approach uses the luminance function:

        GRAY = 0.2126 * R + 0.7152 * G + 0.0722 * B
      

Usage:

function gray = rgb_to_gray ( rgb, equal )

• rgb is an m by n by 3 uint8 (short integers, 0 to 255) array containing the RGB image data; MATLAB's imread() command can be used to create such a dataset from a graphics image file.
• equal is 1 if the R, G and B values are to be weighted equally. Otherwise, a luminance function is used which accounts for the different contributions of each channel to brightness.
• gray is an m by n uint8 array containing the gray scale version of the image.

Licensing:

The information on this web page is distributed under the MIT license.

Languages:

image_rgb_to_gray is available in a MATLAB version and an Octave version.

Related Data and Programs:

image_rgb_to_gray_test

image_threshold, an Octave code which creates a black and white version of a grayscale image by specifying a single threshold value; pixels below this value become black, and above this value they are white.

Reference:

• Jonas Gomes, Luiz Velho,
  Image Processing for Computer Graphics,
  Springer, 1997,
  ISBN: 0387948546,
  LC: T385.G65.
• William Pratt,
  Digital Image Processing,
  Second Edition,
  Wiley, 1991,
  ISBN13: 978-0471857662,
  LC: TA1632.P7.

Source Code:

• image_rgb_to_gray.m, creates a grayscale version of an RGB image.