find out the percentage of pixels having value 1

Hi all,

I have a binary image (with values 0 & 1) of the dimensions 497*597. I want to calculate the fraction (%) of pixels with value 1 in each array of 3*3 pixels out of the full image. can anybody help me in this regard?

Any help is highly appriciated.

Thanks in advance

Bhavini

[Jan]

Do you mean overlapping blocks, such that the first one goes from 1 to 3, the 2nd one from 2 to 4? Or should the block be mutually distinct?

[Bhavini]

Dear Jan,

Yes the blocks must be overlapping, starting from 1 upto 595 horizontally and 1 to 495 vertically.

Answer 1

[Andrei Bobrov]

a = randi([0 1],497,597);
ones_frac = conv2(a,ones(3),'valid')/9*100;

or if you have Image Processing Toolbox

ones_frac = blockproc(a,[3 3],@(x)sum(x.data(:))/9*100);

Answer 2

[Bhomik Luthra]

Lets take a random matrix of size 497*597. I have found the number of 1's in each 3*3 matrix in first horizontal row, u can do it for 497/3 rows by putting a for loop.

a = randint(497,597);

for i = 1:597/3

    p(i)= length(find (a(1:3,3*i-2:3*i)==1))
end

p(i) returns the number of 1's in each 3*3 matrix.

Bhomik Luthra

Answer 3

[Jan]

For a binary image the percentage of 1's is the mean value multiplied by 100.