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Asked: 2026-06-15T20:33:56+00:00

As shown in the attached image [For clarification only], there are three rows of

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As shown in the attached image [For clarification only], there are three rows of lines with random length.
I would like to delete lines which are shorter than a constant N pixels.

Assumptions:

  1. Lines are all in rows
  2. Lines are 1 pixel width
  3. Lines may be connected to borders.

I’m looking for any idea/guide which can help me with this. Thanks.enter image description here

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1 Answer

  1. Editorial Team

    Skipping the possibility of directly handling the binary representation of the underlying image, and thus permitting a pretty fast implementation for this specific task, let us use Mathematical Morphology to (efficiently) solve it.

    All you need here is a erosion with a horizontal line of length n followed by a morphological reconstruction. The former will completely remove lines shorter of length < n. The later will completely recover the eroded lines that were not removed.

    Here is an example with n = 25. I used ones(1, 25) instead of strel('line', 25, 0) as the structuring element because the later doesn’t guarantee that the actual line length is the one specified.

    f = im2bw(imread('https://i.stack.imgur.com/1Uw0x.png'), 0);
g = imerode(f, strel('arbitrary', ones(1, 25)));
h = imreconstruct(g, f);

    Eroded and reconstructed images:

    enter image description here enter image description here

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