A completely different kind of filter — instead of blending intensities, morphology reshapes silhouettes. Slide a small "structuring element" across a binary shape: require a full fit and the shape shrinks (erosion); allow any touch and it grows (dilation). Everything else in this lab — opening, closing, gradients — is just those two ideas combined.
Click anywhere on the image to see the structuring element placed at that exact pixel, and whether erosion/dilation turns it on or off.
A pixel survives only if every cell of the structuring element sits on foreground. One black pixel anywhere under the element kills it. This is why thin lines, small dots, and sharp points vanish first.
A pixel turns on if any cell of the structuring element touches foreground. This is why small gaps, thin cracks, and single missing pixels get patched over.
Erode-then-dilate (opening) permanently deletes anything too small to survive the erosion step. Dilate-then-erode (closing) permanently fills anything too small to survive as a gap. Same two ingredients, opposite order, opposite job.
Your binary image has scattered single-pixel "salt" noise dots everywhere, and the real object also has a couple of small holes punched through it that shouldn't be there. One structuring element, one operation you can run once — which do you reach for?