find out the percentage of pixels having value 1

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Bhavini
Bhavini 2013-6-17
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
  2 个评论
Jan
Jan 2013-6-17
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
Bhavini 2013-6-17
Dear Jan,
Yes the blocks must be overlapping, starting from 1 upto 595 horizontally and 1 to 495 vertically.

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回答（3 个）

Andrei Bobrov
Andrei Bobrov 2013-6-17
编辑：Andrei Bobrov 2013-6-17
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);
Bhomik Luthra
Bhomik Luthra 2013-6-17
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
Jan
Jan 2013-6-17
For a binary image the percentage of 1's is the mean value multiplied by 100.

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