The use of Nargin in Otsu Image Processing

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Michael Yabut
Michael Yabut 2016-7-29
评论： Image Analyst 2016-7-30
I was actually given the full code to use from my professor and all I had to do was process it with a couple of photos. However I'm running into a few problems with the given code and I've tried to understand why it's not working but I think I could use some help. Here it is:
This is the function I think?
%Otsu Thresholding
% [ot,outim]=otsu_thresh(im)
% where im is the grey image (integer 0-255)
% Otsu Thresholding is performed on the image
% ot is the threshold determined
% outim is the image after thresholding
if nargin<1
im=mean(double(imread('10um.jpg')),3);
else
if max(max(imread('10um.jpg')))<=1
im=round(im.*255);
end
end
[height,width]=size(im);
pixels=height*width;
bins=[0:255]+0.5;
N=hist(reshape(im,pixels,1),bins);
Nnorm=N/sum(N); %normalising the bin frequencies to make probabilities
theta=cumsum(Nnorm); %cumulative probability
mu=cumsum(Nnorm.*[0:255]);
%Repeat on the image
sigB2=(mu-mu(256)*theta).^2./(theta.*(1-theta)); %evaluate sigB2 over the t range
[p ot]=max(sigB2); %find the maximum value and the index where it is (this is the Otsu threshold)
and this is the script im supposed to run:
x=(im>ot); %thresholding
figure(1)
imshow(x)
figure(2)
imshow(x)
hist(x);
(I believe there is 0 problems with the actual script just the function)

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回答（1 个）

Image Analyst
Image Analyst 2016-7-29
You're not using the im that was passed in - you're just overwriting it with some predefined image. Try this:
if nargin < 1
im = mean(double(imread('10um.jpg')),3);
else
if max(im(:)) <= 1
% Scal to max possible gray level for its class if it's less than 1.
maxPossibleValue = double(intmax(class(im)))
im = round(maxPossibleValue * double(im));
end
end
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Walter Roberson
Walter Roberson 2016-7-29
You need to put that code inside a "function" -- that is, a .m file that starts with the word "function". nargin is not permitted inside a script (that is, at the command line, or in a .m file that does not start with either "function" or "classdef")
I suggest you just use
if max(im(:)) <= 1
% Scal to max possible gray level for its class if it's less than 1.
maxPossibleValue = double(intmax(class(im)))
im = round(maxPossibleValue * double(im));
end
without the nargin test.
Image Analyst
Image Analyst 2016-7-30
For some reason you commented out the function line. Put it back in:
function [ot,outim]=otsu_thresh(im)

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