ThresholdLocally

Performs LOCAL Otsu thresholding on an image, with a user-specified blocksize.

Description

Performs LOCAL Otsu thresholding on an image; user can specify blocksize. Facilitates the threshold-segmentation of images with uneven illumination, without the need for background normalization.
 
SYNTAX: B = thresholdLocally(A,blksz,varargin)
 
THRESHOLDLOCALLY processes an image, calling graythresh on LOCAL blocks in an image. This facilitates easy thresholding of images with uneven background illumination, for which global thresholding is inadequate. Uses the Image Processing Toolbox function BLOCKPROC (R2009b).
 
INPUTS:
A: Any image (or path/name of an image) suitable for processing with im2bw()

BLKSZ: (Optional) Block size of A, for determination of Otsu thresholding using graythresh(). In the form or [M,N]. Default is as determined by BESTBLK.
OPTIONAL:
1) Any P-V pair accepted by BLOCKPROC.
2) FudgeFactor: a scalar value by which to multiply the local value returned by graythresh.

OUTPUT:
B: Output image
 
EXAMPLE:
img = imread('rice.png');
thresholded = thresholdLocally(img);

Acknowledgements

This file inspired Segment Tool: An Interactive Gui For Segmenting Images.

• Required Products: Image Processing Toolbox
• MATLAB release: MATLAB 7.11 (R2010b)
• Other requirements: Requires Image Processing Toolbox, R2009b or later.

[Nad]

 

[Brett Shoelson]

The NEW version is now available; have at it! Comments/suggestions welcome.

[Brett Shoelson]

Please note: I've submitted a semi-major revision, and am waiting for it to clear. The function will soon accept as optional arguments all PV pairs accepted by BLOCKPROC, and a "fudge factor," by which to multiply the local value returned by graythresh. You may want to wait until the new version is up to download this.