CODEWITHSUNDEEP
matlabimage-processing
user1237226
user1237226

Reputation:

Matlab convert image from gray to binary

İn Matlab, I want to threshold a grayscale image to convert it to a black & white image:

for k=1:Y
  for i=1:X
    if gray(i,k)>T
      gray(i,k)=1;
    else
      gray(i,k)=0;
    end
  end
end

What do you think should be the value of T?

Upvotes: 1

Views: 17304

Answers (3)

Roobie Nuby
Roobie Nuby

Reputation: 1439

Dusty's answer of using Otsu's method is built-in in MATLAB.

The following code is from the MATLAB page about the graythresh function (which implements Otsu's method).

I = imread('coins.png');
level = graythresh(I);
BW = im2bw(I,level);
imshow(BW)

Upvotes: 0

vaichidrewar
vaichidrewar

Reputation: 9621

Inbuilt function im2bw takes level as one of the parameters. So instead of using for loops we can use it for conversion. Default level is 0.5.

From: http://www.mathworks.com/help/images/ref/im2bw.html

im2bw

Convert image to binary image, based on threshold

Syntax

BW = im2bw(I, level)
BW = im2bw(X, map, level)
BW = im2bw(RGB, level)

Upvotes: 0

Oli
Oli

Reputation: 16035

If I were you, I would use the median:

gray=double(gray>median(gray(:)))

PS: you should use this more efficient code in general:

gray=double(gray>T)

Upvotes: 5

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