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Vladimir Botchko botchko@lut.fi

Lecture 7. Image Segmentation Lecture 7. Image Segmentation

Lappeenranta University of Technology (Finland)

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Image segmentation

Detection and discountinuities: point, line and edge detection

Edge linking and boundary detection: local and global (Hough Transform) processing.

Thresholding: illumination, global and adaptive thresholding, optimal thresholding.

Region-oriented segmentation Motion-based segmentation

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Edge models. Step (right) and ramp (left).

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Two ideal edges

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Edge nature. The computer graphics image (left), an image with explicit edge structure

(right).

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Edge nature. The images where almost each pixel belongs to edges

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Edge detection. 3x3 Prewitt operator (close to Sobel).After horizontal mask (upper left), after vertical mask

(upper right), sum for two masks (bottom).

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Edge detection. Sobel (left), Prewitt (right)

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Edge detection. Marr edge detection (Laplacian of Gaussian).

After convolution with a smoothing filter h(r) of =1.5 (left) and =5 (right). Edge detection is given in next slide.

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Edge detection. Marr edge detection.

Zero crossing from above (presented in previous slide) image (right) and the same for left image.

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Edge detection. Original image (grains).

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Edge detection. Sobel (upper left), Prewitt (upper right), Roberts (lower left), Laplacian

of Gaussian (lower right)

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Image segmentation

Detection and discountinuities: point, line and edge detection

Edge linking and boundary detection: local and global (Hough Transform) processing.

Thresholding: illumination, global and adaptive thresholding, optimal thresholding.

Region-oriented segmentation Motion-based segmentation

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Hough Transform

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Hough Transform

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Hough Transform for lines from the previous slide (peaks (highlight dots)

define distance and angle value)

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Image segmentation

Detection and discountinuities: point, line and edge detection

Edge linking and boundary detection: local and global (Hough Transform) processing.

Thresholding: illumination, global and adaptive thresholding, optimal thresholding.

Region-oriented segmentation Motion-based segmentation

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Thresholding

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Thresholding. Illumination role. Left is an original image, right is a nonuniform background estimated from 32x32 pixel

small regions. Background 3-d visualization (lowest)

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Thresholding. Illumination role. Left image is background subructed from original. Right image

after contrast enhancement.

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Thresholding of color images. Segmented land, sky and sea.

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Image segmentation

Detection and discountinuities: point, line and edge detection

Edge linking and boundary detection: e.g. Hough Transform.

Thresholding Region-oriented segmentation Motion-based segmentation

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Region-oriented segmentation

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Region-oriented segmentation

The image taken from Dr. Seppo Leppäjärvi Ph.D. Thesis

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Motion Based Segmentation