image_threshold

image_threshold, a MATLAB 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.

Usage:

function bw = image_threshold ( gray, a )

• gray is an m by n uint8 (short integers, 0 to 255) array containing the grayscale image data; MATLAB's imread() command can be used to create such a dataset from a graphics image file.
• a is a value between 0 and 255 which is used for thresholding.
• bw is an m by n uint8 array containing the gray scale version of the thresholded image. All values in this array are 0 or 255.

Licensing:

The computer code and data files described and made available on this web page are distributed under the MIT license

Languages:

image_threshold is available in a MATLAB version.

Related Data and Programs:

image_boundary, a MATLAB code which reports the pixels which form the boundary between the black and white regions of a simple image.

image_contrast, a MATLAB code which applies image processing techniques to increase the contrast in an image.

image_decimate, a MATLAB code which compresses an image by dropping the even rows and columns of data.

image_denoise, a MATLAB code which applies image processing techniques to remove noise from an image.

image_diffuse, a MATLAB code which uses diffusion to smooth out an image.

image_double, a MATLAB code which doubles the height and width of an image by repeating each row and column.

image_edge, a MATLAB code which demonstrates a simple technique for edge detection in an image.

image_noise, a MATLAB code which adds noise to an image.

image_quantization, a MATLAB code which demonstrates how the kmeans algorithm can be used to reduce the number of colors or shades of gray in an image.

image_rgb_to_gray, a MATLAB function which creates a grayscale version of an rgb image.

image_threshold_test

Reference:

MathWorks documentation for the Image Processing Toolbox is available at https://www.mathworks.com/access/helpdesk/help/pdf_doc/images/images_tb.pdf.

• 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_threshold.m, sets pixels less than or equal to A to black, and pixels greater than A to white.
• image_threshold2.m, sets pixels less than A to black, and pixels greater than B to white, leaving intermediate pixels unchanged.
• image_threshold3.m, sets pixels less than A or greater than B to white, leaving intermediate pixels unchanged.