CODEWITHSUNDEEP
matlab
user1643699
user1643699

Reputation: 169

error in counting white pixels in image,matlab

I have a proplem when dealing with images in matlab, i have a white image and when i try to print the gray level of the image and increment it by 1 , it gives me 255, it never give me 256. and here is the code. and the count is 0.

  function [ count ] = white( I )
    [row,col]=size(I);
    count=0;
    for x=1:row
        for y=1:col
            g=I(x,y);   %the value of the gray level on each pixel
            if((g+1) == 256)
            count=count+1;
            256
        end
    end
  end

Upvotes: 1

Views: 533

Answers (2)

bla
bla

Reputation: 26069

Your image class is probably uint8 and 255 is the maximal value of this class . For example:

 >>  uint8(inf)

ans =

  255

Instead try to cast to a different class, for example I=uint32(I) ...

Following @Aganders3, I'll also offer a solution to your code that doesn't use for loops:

count=sum(I(:)>threshold); % Credit to @Jonas and @Aganders3

where threshold is the gray level you want to threshold

Upvotes: 4

aganders3
aganders3

Reputation: 5945

I think nate is correct on why this is not working.

Also, consider a much simpler solution to your problem (given I is full of integers):

count = sum(vector(I == intmax(class(I))));

Upvotes: 2

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