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Hysteresis Thresholding

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C implementation of Hysteresis Thresholding



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This function takes as parameters a grayscale image (real valued matrix of size x*w*1) and two thresholds (low and high), and returns the hysteresis thresholded version.

Hysteresis thresholding performs the following:
- every value below tLo is set to 0
- every value above tHi is set to 1
- the rest of the pixels are set to 1 if they are 4-way connected to any other 1-valued blob (area), 0 otherwise

It should be pretty straightforward to implement an 8-way connection check, if you want.

To compile and use perform the following:
mex hysteresis.c

Comments and Ratings (6)


I wasn't able to get this to work myself, but programing the functionality in Matlab is very easy

highmask = image>tHi;
lowmask = bwlabel(~(image<tLo));
final = ismember(lowmask,unique(lowmask(highmask)));


Denis (view profile)

There seems to be only 1 set of forward-backward propagation set. It'd be nice if the code was extended to do recursively until nothing changes anymore as suggested on

I guess its really just putting the propagation part in a while loop with checking if any pixel switched from 0 to 1.

Great function otherwise!


make sure grayscale image is of type double

Hi when I compiled and executed this code, I got the following error. I invoked it as TI = hysthresh(GI,0.1,0.4), where GI is a grayscale image.

??? Error using ==> hysthresh
YPRIME requires that Y be a 4 x 1 vector.

I also tried commenting this part in the code and recompiling the code. However, it ran out of memory.

hamid afshang

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