how to compare 2 binary images pixel by pixel
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hello i need help please.
how to compare 2 binary images pixel by pixel? by using "for" in function "compare"?
it show me error (under text) and i do not know how to solve it:
??? Cell contents reference from a non-cell array object.
Error in ==> compare at 4
if BW1{a,b}==BW2{a,b}
Error in ==> com at 9
if compare(BW1,BW2)>100
i have this code:
if true
n=1;
p=2;
i=1;
max=100;
while p <= max
BW1=im2bw(o{n},0.4); % in "o" are colour pictures
BW2=im2bw(o{p},0.4);
if compare(BW1,BW2)>100
c{i}=o{p};
n=p;
p=p+1;
i=i+1;
else
p=p+1;
end
end
end
and function for compare:
if true
function [same] = compare( BW1, BW2 )
for a=1:500
for b=1:500
if BW1{a,b}==BW2{a,b}
same=same+1;
end
end
end
end
end
2 Comments
Accepted Answer
Walter Roberson
on 20 Mar 2014
Change to
if BW1(a,b)==BW2(a,b)
2 Comments
Walter Roberson
on 23 Mar 2014
Edited: Walter Roberson
on 23 Mar 2014
{} is used only to extract something that is in cell array, removing the cell layer. () is used for all other kinds of arrays, such as struct arrays, object arrays, numeric arrays, and char arrays. () is also used for cell arrays when the result is to be left as a cell layer.
More Answers (3)
Image Analyst
on 20 Mar 2014
Lukas, don't loop. It looks like you want to count the number of pixels that are true(1) in both images. If so, just do
bothTrue = BW1 & BW2;
NumPixels = sum(bothTrue(:));
I don't know what you're doing with the "c" and "o" cell arrays and what you're doing with p. It looks like p may likely end up being 100 ("max"). But DO NOT USE max AS THE NAME OF YOUR VARIABLE! max() is a built in function and you'll destroy it if you name your own variable that.
7 Comments
Image Analyst
on 24 Mar 2014
middleRow = ceil(size(BW1, 1)/2);
BW1BottomHalf = BW1(middleRow:end, :);
Then do whatever you want with this half sub-image.
Augustine Ekweariri
on 22 Nov 2016
You can check the difference using Euclidian distance.
test_img = imread('image1.bmp');
input_im = imread('image2.bmp');
minimum =1000;
[row, col] = size(test_img(:,:,1));
distance = zeros(row, col);
for xAxis = 1 : row
for yAxis = 1 : col
distance(xAxis, yAxis) = sqrt((input_im(xAxis, 1) - test_img(yAxis, 1)).^ 2 + (input_im(xAxis, 2) - test_img(yAxis, 2)).^ 2);
end
end
if distance < minimum
minimum = distance;
end
1 Comment
Image Analyst
on 22 Nov 2016
First of all, you made the common beginner mistake of swapping x and y with row and column. The first index of the image arrays is not the x coordinate. It's the y coordinate and it's deceptive to call the y coordinate of input_img "xAxis". If the image is not square and the number of rows is more than the number of columns, your code will throw an error. Like I said, it's a common mistake, so be careful about that.
Secondly the computation doesn't make sense. You're taking the "distance" between the delta of the first columns and the delta of the second columns. Not only doesn't that make sense, but it ignores all columns from 3 onwards.
Third, using minimum, which goes from a scalar to a 2-D array, is unneeded and never even used.
And finally the whole loop thing could be vectorized into a single line of code.
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