How to find the highest 5 adjacent pixels in a matrix?

1 view (last 30 days)
Hi, I am trying to find the 5 highest value pixels in a matrix. The drawback is that the pixels need to be connected. So, if I have:
X=
9.1113 64.762 23.623 77.029 25.644
57.621 67.902 11.94 35.022 61.346
68.336 63.579 60.73 66.201 58.225
54.659 94.517 45.014 41.616 54.074
42.573 20.893 45.873 84.193 86.994
64.444 70.928 66.194 83.292 26.478
I would want something like:
B=
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 45.873 84.193 86.994
0 0 66.194 83.292 0
Any ideas on how to achieve this?
Thank you in advance!
  2 Comments
Guillaume
Guillaume on 23 Apr 2018
You need to explain what these particular 5 values are chosen (and not 5 that are connected to the max 94.517 for example).
You also need to state what degree of connectivity you want. 4-connected or 8-connected?
turningpoint
turningpoint on 23 Apr 2018
I want the 5 connected pixels whose sum is the highest in the matrix. That's why the pixel with the value 94 is not include in the answer. I want 8-connected pixs.

Sign in to comment.

Accepted Answer

Guillaume
Guillaume on 23 Apr 2018
The only way I can think of solving this is to calculate the convolution of your matrix with all possible 5 pixel patterns. You only need to generate the patterns in one quadrant, but with 8-connected components, it's still a lot of patterns:
conv2(yourimage, [1 1 1 1 1], 'valid')
conv2(yourimage, [1 1 1 1 0; 0 0 0 0 1], 'valid')
...
conv2(yourimage, eye(5), 'valid');
...
conv2(yourimage, [1 0; 1 0; 1 0; 1 0; 0 1], 'valid')
conv2(yourimage, [1; 1; 1; 1; 1], 'valid')
The location of the maximum of each convolution is the top-left corner of the corresponding 5 pixel pattern with the maximum sum. The maximum of these maximum is what you're looking for.
  1 Comment
turningpoint
turningpoint on 26 Apr 2018
I guess that's my best option. Eventhough I was trying to avoid it. Thank you!

Sign in to comment.

More Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!