Action shot function with multiple images

Asked by Sara Foster on 9 Sep 2019

Latest activity Commented on by Peter Bier on 11 Sep 2019

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My function uses multiple RGB images as a 1xn 1D cell array and the output creates an action shot.

For example, this will consist of 6 different images containing one moon, but when combined it creates one image (an action shot).

So far I'm using a nested for loop for the rows, columns and number of images but is there any other way to approach this?

1 Comment

Sara Foster on 10 Sep 2019

I asked what the process is for the code, I’m writing my own code but I was unsure how to approach it. (:

1 Answer

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Answer by Matt J on 9 Sep 2019

Edited by Matt J on 9 Sep 2019

Accepted Answer

Yes, here is an approach that uses no loops,

Image4D=double(cat(4,ImageCell{:}));
MedianImage = median(Image4D,4);
[~,idx]= max(vecnorm(Image4D-MedianImage,2,3),[],4);
mask=idx==reshape(1:numel(ImageCell),1,1,1,[]);
result=uint8( sum(Image4D.*mask,4)  );

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Matt J on 9 Sep 2019

Here's one way you could incorporate a loop:

Image4D=double(cat(4,ImageCell{:}));
MedianImage = median(Image4D,4);
[~,idx]= max(vecnorm(Image4D-MedianImage,2,3),[],4);
result=0;
for i=1:numel(ImageCell)
    result=result+Image4D(:,:,:,i).*(idx==i);
    
end
result=uint8( result );

Matt J on 9 Sep 2019

Here's another way with a double for-loop. This one might even be more efficient than the original because it allocates no memory for a mask.

 Image4D=double(cat(4,ImageCell{:}));
MedianImage = median(Image4D,4);
[~,idx]= max(vecnorm(Image4D-MedianImage,2,3),[],4);
result=num2cell(zeros(size(MedianImage),'uint8'),[1,2]);
for i=1:numel(ImageCell)%images
    loc=(idx==i);
    for j=1:3 %color channels
        
        tmp=Image4D(:,:,j,i);
        
        
        result{j}(loc)=tmp(loc);
        
    end
end
result=cell2mat(result);

Peter Bier on 11 Sep 2019

Interesting approach, although well beyond the scope of what we've taught our students.

This is a reminder to all 131 students that as mentioned in class you need to write your own code for the project that is due shortly (rather than getting code written by one of the kind folks who answer questions on the mathworks forum). Copying any of the supplied code from above and submitting it as your own will be detected by our plagiarism detection software when we come to mark the project.

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