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Vladimir Botchko botchko@lut.fi

Lappeenranta University of Technology (Finland). Lecture 3. Image Enhancement in Spatial Domain. Vladimir Botchko botchko@lut.fi. Image Enhancement. Simple intensity transformations Histogram processing (equalization) Image subtraction Image averaging

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Vladimir Botchko botchko@lut.fi

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  1. Lappeenranta University of Technology (Finland) Lecture 3. Image Enhancement in Spatial Domain Vladimir Botchko botchko@lut.fi

  2. Image Enhancement • Simple intensity transformations • Histogram processing (equalization) • Image subtraction • Image averaging • Spatial filtering (smoothing, sharpening) • Enhancement. First derivative (gradient) • Example of manual edge enhancement: • made by artist.

  3. Simple intensity transformations • Contrast stretched

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

  5. Image Enhancement • Simple intensity transformations • Histogram processing • Image subtraction • Image averaging • Spatial filtering (smoothing, sharpening) • Enhancement. First derivative (gradient).

  6. Histogram equalization

  7. Image Enhancement • Simple intensity transformations • Histogram processing • Image subtraction • Image averaging • Spatial filtering (smoothing, sharpening) • Enhancement. First derivative (gradient).

  8. Image subtraction

  9. Image Enhancement • Simple intensity transformations • Histogram processing • Image subtraction • Image averaging • Spatial filtering (smoothing, sharpening) • Enhancement. First derivative (gradient).

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

  11. Order-statistics filter for binary images (when numl=5 then it is median) • Rank filter is used for smoothing after recognition for segmentation. Simple Matlab code is here:

  12. Order-statistics filter • First is median filtering result (rank 5 for 3x3 window). Upper part is input image • lower part is smoothed image

  13. Order-statistics filter • Then the rank (rank 3 for 3x3 window). Original image upper, smoothed image is lower

  14. Sharpening • Second Derivatives. Laplacian

  15. Image Enhancement • Simple intensity transformations • Histogram processing • Image subtraction • Image averaging • Spatial filtering (smoothing, sharpening) • Enhancement. First derivative (gradient).

  16. Median filter and Sobel operator • Gray-level images (from left to right from top to bottom):original texture synthetic (computer generated) image,the result of recognition corrupted by classification errors, median filtering, edge extraction through Sobel operator, superposition a gray level image and image with edges.

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