- Neighbourhood filters
- Rank filters
This module explains how filters can be used to change size and shape of objects in the image.
- Understand how to design morphological filters using rank filters
- Execute morpholofical filters on binary or grayscale images and explain the output
graph TD image --> max1[max] image --> min1[min] image --> max2[max] image --> min2[min] image --> d subgraph rank filter sequence max2 --> min3[min] min2 --> max3[max] max1 min1 d[max - min] end max1 --> dilation min1 --> erosion max3 --> opening min3 --> closing d --> gradient subgraph morphological filter name dilation erosion opening closing gradient end
[*] Concept map above assumes bright objects on dark background. For dark objects on bright background effect of min and max filters inverses
Activity: Explore erosion and dilation on binary images
- Open image: xy_8bit_binary__two_spots_different_size.tif
- Explore how structures grow and shrink, using erosion and dilation
Activity: Explore opening and closing on binary images
- Open image: xy_8bit_binary__for_open_and_close.tif
- Explore effects of morphological closing and opening:
- closing can fill holes
- closing can connect gaps
- opening can remove thin structures
Fill in the blanks, using those words: shrinks, increases, decreases, enlarges.
- An erosion _____ objects in a binary image.
- An erosion in a binary image _____ the number of foreground pixels.
- A dilation in a grayscale image _____ the average intensity in the image.
- A dilation _____ objects in a binary image.
True of false? Discuss with your neighbour!
- Morphological openings on binary images can decrease the number of foreground pixels.
- Morphological closings on binary images never decreases the number of foreground pixels.
- Performing a morphological closing a twice in a row does not make sense, because the second closing does not further change the image.