index.md (1481B)
1 +++ 2 title = 'Image processing' 3 +++ 4 # Image processing 5 Problems: 6 1. Acquired signals are often noisy 7 2. Context information is often hidden 8 9 Below are options for image processing. 10 11 [Point processing](./point-processing) 12 13 [Neighborhood processing](./neighborhood-processing) 14 15 [Morphological operations](./morphological-operations) 16 17 18 ## Windowing 19 Select a region of interest — user defined region within the image. 20 Then crop (resize) the image. 21 22 ## Segmentation 23 Partitioning an image into separate objects, main vs background. 24 Can be done by: 25 26 - Edge detection 27 - edge — local discontinuity in pixel value that exceeds given threshold 28 - consists of creating binary image where non-background pixel values are object boundaries 29 30  31 32 - can be obtained by correlation with a kernel 33 - Prewitt 34 - Canny 35 - Sobel 36 37  38 39 ## BLOB analysis 40 BLOB — binary large object (group of connected pixels in binary image) 41 42 connectivity decides which pixels are neighbours (4-connectivity, 8 connectivity) 43 44 set of allpixels which are connected to a given pixel is a connected component or BLOB 45 46  47 48 extracting connected components is called labelling, each connected component is given a label. 49 50 0 is background, then 1,2,3,… 51 52 in MATLAB, bwlabel returns matrix with labels and number of BLOBs