Image processing

Problems:

1. Acquired signals are often noisy
2. Context information is often hidden

Below are options for image processing.

Point processing

Neighborhood processing

Morphological operations

Windowing

Select a region of interest — user defined region within the image. Then crop (resize) the image.

Segmentation

Partitioning an image into separate objects, main vs background. Can be done by:

• Edge detection

  • edge — local discontinuity in pixel value that exceeds given threshold
  • consists of creating binary image where non-background pixel values are object boundaries

  

  • can be obtained by correlation with a kernel

    • Prewitt
    • Canny
    • Sobel

    

BLOB analysis

BLOB — binary large object (group of connected pixels in binary image)

connectivity decides which pixels are neighbours (4-connectivity, 8 connectivity)

set of allpixels which are connected to a given pixel is a connected component or BLOB

extracting connected components is called labelling, each connected component is given a label.

0 is background, then 1,2,3,…

in MATLAB, bwlabel returns matrix with labels and number of BLOBs