IMAGE_QUANTIZATION
Reduce Number of Colors in an Image

IMAGE_QUANTIZATION is a MATLAB library which demonstrates how the KMEANS algorithm can be used to reduce the number of colors or shades of gray in an image.

Licensing:

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

Related Data and Programs:

CELL_DETECTION_TASKS, a MATLAB program which creates modified versions of a sequence of gray-scale TIF files containing images of cells; the process of each file is carried out independently, using the "task" feature of MATLAB's parallel computing toolbox.

COLOR_REMOTE, a MATLAB program which carries out the color segmentation of an image in parallel, via SPMD commands; this includes instructions on how to run the job, via MATLAB's BATCH facility, on a remote system such as Virginia Tech's ITHACA cluster.

CONTRAST_SPMD, a MATLAB program which demonstrates the SPMD parallel programming feature for image operations; the client reads an image, the workers increase contrast over separate portions, and the client assembles and displays the results.

CONTRAST2_SPMD, a MATLAB program which demonstrates the SPMD parallel programming feature for image operations; this improves the contrast_spmd program by allowing the workers to share some data; this makes it possible to eliminate artificial "seams" in the processed image.

IMAGE_COMPONENTS, a MATLAB library which seeks the connected "nonzero" or "nonblack" components of an image or integer vector, array or 3D block.

IMAGE_CONTRAST, a MATLAB program which applies image processing techniques to increase the contrast in an image.

IMAGE_DENOISE, a MATLAB program which applies image processing techniques to remove noise from an image.

IMAGE_DIFFUSE, a MATLAB library which uses diffusion to smooth out an image.

IMAGE_EDGE, a MATLAB library which demonstrates a simple procedure for edge detection in images.

IMAGE_NOISE, MATLAB programs which add noise to an image.

IMAGE_RGB_TO_GRAY, MATLAB programs which makes a grayscale version of an RGB image.

IMAGE_THRESHOLD, MATLAB programs which make a black and white version of a grayscale image by setting all pixels below or above a threshold value to black or white.

KMEANS, a MATLAB library which contains several different algorithms for the K-Means problem.

Reference:

1. Jonas Gomes, Luiz Velho,
   Image Processing for Computer Graphics,
   Springer, 1997,
   ISBN: 0387948546,
   LC: T385.G65.

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

Source Code:

• grayscale_quantization.m, carries out KMEANS quantization on a grayscale image.
• timestamp.m, prints the current YMDHMS date as a timestamp.

Examples and Tests:

• image_quantization_test.m, a program which calls all the tests.
• image_quantization_test_output.txt, the output from the tests.
• image_quantization_test01.m, tests grayscale_quantization on an image.

CASABLANCA is a still from the movie "Casablanca".

• casablanca.png, a grayscale PNG image, using 256 shades.
• casablanca_histogram.png, a histogram of the grayscale shades.
• casablanca_ten.png, the image using only 10 shades.
• casablanca_three.png, the image using only three shades.

SNAP is a snapshot of a mother and daughter.

• snap.png, a grayscale PNG image, using 208 shades.
• snap_histogram.png, a histogram of the grayscale shades.
• snap_ten.png, the image using only 10 shades.
• snap_three.png, the image using only three shades.

You can go up one level to the MATLAB source codes.