Image processing.html (4379B)
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3 <html> 4 5 <head><link rel="stylesheet" href="sitewide.css" type="text/css"> 6 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 7 <meta name="exporter-version" content="Evernote Mac 7.5.2 (457164)" /> 8 <meta name="altitude" content="-0.9683055877685547" /> 9 <meta name="author" content="Alex Balgavy" /> 10 <meta name="created" content="2017-11-07 11:04:35 +0000" /> 11 <meta name="latitude" content="52.33476618838052" /> 12 <meta name="longitude" content="4.866821194517779" /> 13 <meta name="source" content="desktop.mac" /> 14 <meta name="updated" content="2017-12-19 22:01:20 +0000" /> 15 <title>Image processing</title> 16 </head> 17 18 <body> 19 <div>Problems:</div> 20 <div> 21 <ol> 22 <li>Acquired signals are often noisy</li> 23 <li>Context information is often hidden</li> 24 </ol> 25 <div><br /></div> 26 </div> 27 <div>Below are options for image processing.</div> 28 <div><br /></div> 29 <div><a href="Point processing.html"">Point processing</a></div> 30 <div><a href="Neighborhood processing.html"">Neighborhood processing</a></div> 31 <div><a href="Morphological operations.html">Morphological operations</a></div> 32 <div><br /></div> 33 <div><span style="font-weight: bold;">Windowing</span></div> 34 <div>Select a region of interest — user defined region within the image.</div> 35 <div>Then crop (resize) the image.</div> 36 <div><br /></div> 37 <div><span style="font-family: "Helvetica Neue"; font-weight: bold;">Segmentation</span></div> 38 <div><span style="font-family: "Helvetica Neue";">Partitioning an image into separate objects, main vs background.</span></div> 39 <div><span style="font-family: "Helvetica Neue";">Can be done by:</span></div> 40 <div> 41 <ul> 42 <li><span style="font-family: "Helvetica Neue";">Edge detection</span></li> 43 <ul> 44 <li><span style="font-family: "Helvetica Neue";">edge — local discontinuity in pixel value that exceeds given threshold</span></li> 45 <li><span style="font-family: "Helvetica Neue";">consists of creating binary image where non-background pixel values are object boundaries</span></li> 46 </ul> 47 </ul> 48 </div> 49 <blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;"> 50 <blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;"> 51 <div> 52 <font face="Helvetica Neue"><img src="Image%20processing.resources/screenshot.png" height="245" width="467" /><br /></font> 53 </div> 54 </blockquote> 55 </blockquote> 56 <div> 57 <ul> 58 <ul> 59 <li><span style="font-family: "Helvetica Neue";">can be obtained by correlation with a kernel</span></li> 60 <ul> 61 <li><span style="font-family: "Helvetica Neue";">Prewitt</span></li> 62 <li><span style="font-family: "Helvetica Neue";">Canny</span></li> 63 <li><span style="font-family: "Helvetica Neue";"> Sobel</span></li> 64 </ul> 65 </ul> 66 </ul> 67 </div> 68 <blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;"> 69 <blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;"> 70 <div><img src="Image%20processing.resources/screenshot_2.png" height="292" width="474" /><br /></div> 71 </blockquote> 72 </blockquote> 73 <div><br /></div> 74 <div><br /></div> 75 <div><br /></div> 76 <div><br /></div> 77 <div><span style="font-weight: bold;">BLOB analysis</span></div> 78 <div>BLOB — binary large object (group of connected pixels in binary image)</div> 79 <div>connectivity decides which pixels are neighbours (4-connectivity, 8 connectivity)</div> 80 <div>set of allpixels which are connected to a given pixel is a connected component or BLOB</div> 81 <div><br /></div> 82 <div><img src="Image%20processing.resources/screenshot_1.png" height="107" width="367" /><br /></div> 83 <div><br /></div> 84 <div>extracting connected components is called labelling, each connected component is given a label.</div> 85 <div>0 is background, then 1,2,3,…</div> 86 <div>in MATLAB, <span style="font-family: "Courier New";">bwlabel </span><span style="font-family: "Helvetica Neue";">returns matrix with labels and number of BLOBs</span></div> 87 </body> 88 89 </html>