lectures.alex.balgavy.eu

Lecture notes from university.
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      1 +++
      2 title = 'Point processing'
      3 +++
      4 # Point processing
      5 A simple function applied to each value — e.g. to lighten, y = x+C
      6 
      7 Ex: change brightness of every pixel in the same way
      8 
      9 ![screenshot.png](3324add035d108efc1dc36a5adc53f9f.png)
     10 
     11 ```
     12 b = imread(‘filename.bmp’);
     13 b1 = imadd(b,128);
     14 ```
     15 
     16 ## Type conversion
     17 From RGB to grayscale (24 bits -> 8 bits)
     18 
     19 ```
     20 I = imread(‘filename.bmp’);
     21 J = rgb2gray(I);
     22 ```
     23 
     24 ## Histogram stretching
     25 
     26 A histogram graphs the amount of times each value from 0 to 255 occurs in an image.
     27 
     28 You can stretch a histogram to equalise the image
     29 
     30 ![screenshot.png](4f05a88f44157b44d30209a3fa3a1941.png)
     31 
     32 ## Thresholding
     33 
     34 - a gray scale image can be converted into binary (B&W)
     35 - choose a grey level T (threshold), change each pixel based on relation to T
     36 - white if >T, black if ≤T
     37 
     38 ![screenshot.png](14678296b2a9a5e2df1e024513278322.png)