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# Image segmentation

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### Image segmentation

1. 1. Study and Implementation of Watershed Algorithm using MATLABSupervisor– Prof. Sanjeev Kumar By– Mukul Jindal 1
2. 2. Watershed AlgorithmThe watershed transformation is a technique forsegmenting digital images that uses a type ofregion growing method based on an image gradient. Itthus effectively combines elements fromboth the discontinuity and similarity methods describedbelow. 2
3. 3. What is Image SegmentationThe goal of image segmentation is to reduce the number of colours in the inputreference image and then group neighbouring pixels of similar colour together toform bounded segmentsSegmentation subdivides an image into its constituent regions or groups.The level to which the subdivision is carried depends on the problem beingsolved.That is, segmentation should stop when the objects of interest in an applicationhave been isolated.e.g. automated inspection of electronic assemblies; specific anomalies; missingcomponents or broken connection paths. 3
4. 4. Image SegmentationalgorithmIt is based on two basic properties of intensity values :discontinuity and similarityFirst Category : Abrupt changes in intensity.Second Category : Partitioning of regions which aresimilar according to a set of predefined criteria. e.g.thresholding, region growing, region splitting and merging. 4
5. 5. First Category is further subdividedinto-•Points•Lines•Edges 5
6. 6. Detection of discontinuitiesPoints, lines, edgesThe most common wayR = w1*z1 + w2*z2 + ……+ w9*z9 6
7. 7. Point detection R  T T = Threshold 7
8. 8. Point detection(b) X-ray image (c) Result of (d) Result of pointof a turbine blade point detection detection maskwith porosity mask with threshold 8
9. 9. Line detection– A Suitable Mask in desired direction– Thresholding 9
10. 10. Line detection • Example:-45º Mask Thresholding 10
11. 11. Edge Detection– Two Mathematical model 11
12. 12. Edge Detection Gray level profile First derivative Second derivative 12
13. 13. Gradient OperatorsY-direction X-direction 13
14. 14. Diagonal Edge 45-Direction-45-Direction 14
15. 15. Diagonal edge detection 15
16. 16. Things done so far• Read about different Image Segmentation processes.• Working my way towards implementing Watershedalgorithm using MATLAB. 16
17. 17. Things to be done• Use preprocessing method to be implemented onimages.• Implement Watershed Algorithm• Analyse and record the difference after processing. 17
18. 18. Test Result Expected from WatershedAlgorithm Test image After Watershed Algorithm 18
19. 19. References -• Paul R. Hill. Wavelet Based Texture Analysis andSegmentation for Image Retrieval and Fusion. PhD thesis,University of Bristol, March 2002.• Richard E. Woods and R.C. Gonzalez. Digital ImageProcessing. Pearson Education, 2005. 19
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