1. 1 Vladimir Botchko botchko@lut.fi Lecture 4. Image Enhancement Lappeenranta University of Technology (Finland)

2. 2 Image Enhancement n Simple intensity transformations n Histogram processing n Image subtraction n Image averaging n Spatial filtering (smoothing, sharpening) n Enhancement in the frequency domain n Example of manual edge enhancement:

3. 3 Simple intensity transformations n Contrast stretched

4. 4 Simple intensity transformations n Intensity level slicing: n Original image (top) n Thresholded (left) n Gray-level slicing (lower right)

5. 5 Image Enhancement n Simple intensity transformations n Histogram processing n Image subtraction n Image averaging n Spatial filtering (smoothing, sharpening) n Enhancement in the frequency domain

6. 6 Histogram equalization

7. 7 Image Enhancement n Simple intensity transformations n Histogram processing n Image subtraction n Image averaging n Spatial filtering (smoothing, sharpening) n Enhancement in the frequency domain

8. 8 Image subtraction

9. 9 Image Enhancement n Simple intensity transformations n Histogram processing n Image subtraction n Image averaging n Spatial filtering (smoothing, sharpening) n Enhancement in the frequency domain

10. 10 Image averaging. Spatial filtering (smoothing) n Original image (upper left) n Original + noise (upper right) n Smoothed image (lower right) n Median smoothing (lower left)

11. 11 Sharpening n Deatil/edge enhancement like unsharp masking

12. 12 Image Enhancement n Simple intensity transformations n Histogram processing n Image subtraction n Image averaging n Spatial filtering (smoothing, sharpening) n Enhancement in the frequency domain

13. 13 Enhancement in the frequency domain n High pass filtering

14. 14 Enhancement in the frequency domain n Low pass filtering