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Lecture Digital image processing - Lecture 15: Image enhancement

This chapter presents the following content: Image differencing, averaging of the images, mask processing, linear smoothing operation, mask processing, linear smoothing operation, median filter, sharpening spatial filter. | Digital Image Processing CSC331 Image Enhancement 1 Summery of previous lecture Image differencing Averaging of the images Mask processing Linear smoothing operation 2 Todays lecture Mask processing Linear smoothing operation Median filter Sharpening spatial filter 3 Mask processing A neighborhood of size more than 1, then the kind of operation that we are going to have that is known as mask processing operation. Linear smoothing operation Nonlinear operation (which is based on the statistical features of the image known as the median filtering operation) The sharpening filter 4 Mask use 5 Mask process 6 3 by 3 neighborhood around a pixel location (x, y) 7 Mask operation 8 W I,j are also called coefficients 9 10 11 12 Smoothing operation Image smoothing is also called the image averaging operation. Is a special filtering operation where the value at a particular location (x, y) in the processed image is the average of all the pixel values in the neighborhood of x and y. So, because it is the average, this is also known as averaging filter and later on we will see that this averaging filter is nothing but a low pass filter. 13 Image smoothing 14 Filter to avoid the blur effect 15 Smoothing spatial filter Expression 16 Spatial Lowpass Filter 17 Spatial Lowpass Filter 18 Median filter Non-Linear Filtering of Images The median filter is conceptually similar to an averaging kernel. An averaging kernel produces an output pixel g(i,j) that is the mean intensity of a neighborhood around f(i,j). The output is simply the middle value of the sorted list. 19 The median filter is ideal for removing impulsive noise, sometimes referred to as "salt and pepper" or "shot" noise This type of noise manifests itself as outlier pixel intensities, completely independent of signal content. Because of the need to sort the values within the sliding window, The median filter can be quite costly to implement – however they are preferred to a smoothing filter in these cases because they . | Digital Image Processing CSC331 Image Enhancement 1 Summery of previous lecture Image differencing Averaging of the images Mask processing Linear smoothing operation 2 Todays lecture Mask processing Linear smoothing operation Median filter Sharpening spatial filter 3 Mask processing A neighborhood of size more than 1, then the kind of operation that we are going to have that is known as mask processing operation. Linear smoothing operation Nonlinear operation (which is based on the statistical features of the image known as the median filtering operation) The sharpening filter 4 Mask use 5 Mask process 6 3 by 3 neighborhood around a pixel location (x, y) 7 Mask operation 8 W I,j are also called coefficients 9 10 11 12 Smoothing operation Image smoothing is also called the image averaging operation. Is a special filtering operation where the value at a particular location (x, y) in the processed image is the average of all the pixel values in the neighborhood of x and y. So, because