Image Filtering with GLSL

# Image Filtering with GLSL

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## Image Filtering with GLSL

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1. Image Filtering with GLSL DI1.03 蔡依儒

2. Outline • Convolution • Convolution implementation using GLSL • Commonly used convolution filter • Mean Filter • Gaussian Filter • Laplacian Filter • Sharpness Filter

3. Convolution1 • Convolution • an operation in which the final pixel is the weighted sum of the neighboring pixels • Convolution kernel • a matrix which gives some weight to each one of the neighbor pixels • filter, mask, kernel, template, or window

4. Convolution2

5. Convolution implementation using GLSL

6. Mean Filter • Most commonly used for the image noise elimination • eliminating pixel values which are unrepresentative of their surroundings

7. Gaussian Filter1 • A kind of Lowpass filters • Used to blur an image and remove detail and noise 1/16 2/16 1/16 2/16 4/16 2/16 2/16 1/16 1/16

8. Gaussian Filter2

9. Gaussian Filter3 • Results of smoothing with square filter masks of sizes n = 3, 5, 9, 15, and 35, respectively • The black squares at the top are of sizes 3, 5, 9, 15, 25, 35, 45, and 55 pixels, respectively

10. Laplacian Filter1 • Used for the image edges detection 0 1 0 1 -4 1 1 0 0

11. Laplacian Filter2

12. Sharpness Filter • Used to increase and to make stand out the details of an image 0 -1 0 -1 -1 -1 -1 -1 5 9 -1 -1 -1 -1 0 0 -1 -1

13. 馬賽克

14. Reference • http://www.ozone3d.net/tutorials/image_filtering.php • http://www.cee.hw.ac.uk/hipr/html/filtops.html • Digital Image Processing 2nd Edition • by Gonzalez and Woods • Prentice Hall • http://big5.yesky.com/b5/www.yesky.com/SoftChannel/72342371928702976/20041028/1869312.shtml