How to draw a black border around the image

Question

How can I crop the image such that it will only contain the leaf and not have the noise part?

Do you have the image processing toolbox? Which MATLAB version are you using? There seems to be a discrepancy between the title of the topic and what you're asking. Do you want to have an image with a smaller size, or will the same size, only keeping the leaf, will do? Is the object you want to keep always the largest? — Dev-iL, Mar 17 '17 at 07:00

score 4 · Answer 1 · edited Sep 27 '17 at 19:06

If you have the Image Processing Toolbox, you can do something like this:

Morphologically open the image (to remove salt and pepper noise).
Convert the image to binary.
Detect the largest contiguous area (presumably the object-of-interest).
Set all other pixels to an "ignored value" (in this case, 255).
"Crop" the original image by means of indexing the bounding box.

function out = q42849445
img = imread('https://i.stack.imgur.com/hTtqz.jpg');
bw = ~imopen(logical(img),strel('disk',10));
stats = regionprops(bw,'Area','SubarrayIdx');
[~,I] = max([stats.Area]);
for ind = setdiff(1:numel(stats),I)
  img(stats(ind).SubarrayIdx{:}) = 255;
end
out = img(stats(I).SubarrayIdx{:});

The result (using imshow):

How to draw a black border around the image

1 Answers1