Point processing.html (2691B)
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><head><link rel="stylesheet" href="sitewide.css" type="text/css"><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/><meta name="exporter-version" content="Evernote Mac 7.5.2 (457164)"/><meta name="altitude" content="-0.4378171265125275"/><meta name="author" content="Alex Balgavy"/><meta name="created" content="2017-12-19 19:53:28 +0000"/><meta name="latitude" content="52.37364976172622"/><meta name="longitude" content="4.836290468415996"/><meta name="source" content="desktop.mac"/><meta name="updated" content="2017-12-19 19:57:57 +0000"/><title>Point processing</title></head><body><div>A simple function applied to each value — e.g. to lighten, y = x+C<br/></div><div>Ex: change brightness of every pixel in the same way</div><div><br/></div><div><img src="Point%20processing.resources/screenshot_1.png" height="199" width="407"/> </div><div><br/></div><div><span style="font-family: "Courier New";">b = imread(‘filename.bmp’);</span></div><div><span style="font-family: "Courier New";">b1 = imadd(b,128);</span></div><div><br/></div><div><b>Type conversion</b></div><div>From RGB to grayscale (24 bits -> 8 bits)</div><div><br/></div><div><span style="font-family: "Courier New";">I = imread(‘filename.bmp’);</span></div><div><span style="font-family: "Courier New";">J = rgb2gray(I);</span></div><div><br/></div><div><span style="font-family: "Helvetica Neue";"><b>Histogram stretching</b></span></div><div><span style="font-family: "Helvetica Neue";">A histogram graphs the amount of times each value from 0 to 255 occurs in an image.</span></div><div><span style="font-family: "Helvetica Neue";">You can stretch a histogram to equalise the image</span></div><div><br/></div><div><img src="Point%20processing.resources/screenshot_2.png" height="254" width="328"/><br/></div><div><br/></div><div><span style="font-family: "Helvetica Neue";"><b>Thresholding</b></span></div><ul><li><span style="font-family: "Helvetica Neue";">a gray scale image can be converted into binary (B&W)</span></li><li><span style="font-family: "Helvetica Neue";">choose a grey level T (threshold), change each pixel based on relation to T</span></li><li><span style="font-family: "Helvetica Neue";">white if >T, black if ≤T</span></li></ul><div><br/></div><div><img src="Point%20processing.resources/screenshot.png" height="275" width="664"/><br/></div><div><br/></div></body></html>