1. Image Filtering with GLSL

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

3. Convolution1 Convolution Convolution kernel
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
Also known as filter, mask, kernel, template, or window

4. Convolution2

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

6. Gaussian Filter1 A kind of lowpass filter
Used to blur an image and remove detail and noise
1/16
4/16
2/16

7. Gaussian Filter2

8. Gaussian Filter3
Filter size 3 5 9 15 35

9. Laplacian Filter1
Used for the image edges detection -4 1

10. Laplacian Filter2

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

12. Sobel Filter1
Edge detection: compute opposite of the (color) gradient vector, or the norm of this vector

13. Sobel Filter2 Height map to Normal map Using Sobel Filters (ref)
Encode [-1,1]3 to [0,1]3
Note: in glsl, I swap the first and third rows of Gy, as the t axis points up!

14. 馬賽克

17. Fragment Shader (1/2) Array constructor (assume texture 256x256)
step_w = 1/256
Array constructor

18. Fragment Shader (2/2)