Image Filtering. Problem! Noise is a problem, even in images! Gaussian NoiseSalt and Pepper Noise.

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Presentation transcript:

Image Filtering

Problem! Noise is a problem, even in images! Gaussian NoiseSalt and Pepper Noise

What to do? Try to think of ways to remove the noise! Gaussian NoiseSalt and Pepper Noise

Smoothing The most obvious and easy way to remove the noise is by averaging. We can average pixels of a specific neighborhood by convolution with an averaging filter.

Smoothing Convolution is a simple mathematical operation.

Smoothing Smoothing using 3x3 mean filter. Gaussian NoiseSalt and Pepper Noise

Gaussian Filter Gaussian filter is more natural!

Gaussian Filter Gaussian mask with σ=1.

Gaussian Filter Gaussian filter is more natural! Gaussian NoiseGaussian 5x5 Filter

Median Filter Median filter operation.

Median Filter Removing Salt and Pepper Noise using Median Filtering. Salt and Pepper Noise3x3 Median Filter

Edge Detection Finding the edges of images is a very useful tool. How do we find the edges in images?

Edge Detection Yes you’re right, derivatives!!

Edge Detection We use image filtering to find edges. There are many masks: Prewitt, Sobel, Roberts Roberts Sobel Prewitt

Edge Detection The gradient magnitude and gradient angle can be calculated as follows: