Machine Vision Blob ApplicationsPaul Stephenson

Oct 20, 2014

Matlab Demo-Blob Centroid and Perimeter

What is Matlab Doing?

What is Matlab Doing?Centroid

“In mathematical terms the center of mass, (xc,yc) is calculated as

where N is the number of pixels in the Bloband Xi and y are the x and y coordinates of the N pixels, respectively.”

What is Matlab Doing?Perimeter

Perimeter Algorithm Common Steps1. Create Binary Blob from image2. Close holes in object using a method such as

dilation3. Use an edge detection algorithm to find the

edge of the object4. Count number of pixels in detected edge.

Technical Paper:Perimeter AlgorithmsThere are many perimeter Algorithms which give

varying levels of accuracyFirst we detect the edge using one of many methods.

1. Canny Method (perhaps the most common method)2. Sobel Method3. Prewitt Method4. Roberts Method5. Laplacian of Gaussian method6. Zero Cross Method

Technical Paper:Perimeter AlgorithmsNow we have several different methods to find the perimeter.

The simplest is to count the number of squares on the edge

The next is to adjust for the diagonals

Another is to go around the very edge of the pixels and cut across diagonally from the side center points.

Each of these methods will give increasing accuracy, but will take more complex programming and more processing power.

Why do we care?-Real World Applications_______ Detection or

_______Recognition=Probably uses some sort of blob or perimeter algorithm.

As for AutomationMost automation vision systems need to

recognize certain features or parts. This is usually done using some sort of blob algorithm.

Other examplesKinect Video

Vendors and PricingRoboRealmNational InstrumentsDatalogicTeledyne DalsaMVTecCognexAnd Many morePrices Range from $50-$7000+

It all depends on what you need it to do

The Future of Blob AlgorithmsIncreasing use in automationMobile device and home computer

integrationHome customization of motion controls

References http://www.mathworks.com/matlabcentral/fileexchange/25157-image-segmentation-

tutorial---blobsdemo--

http://www.mathworks.com/help/vision/ref/blobanalysis.html Methods to estimate areas and perimeters of blob-like objects: a comparison (1994),

Luren Yang , Fritz Albregtsen , Tor Lgnnestad , Per Grgttum ; dhttp://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.143.4018

Undergraduate Topics in Computer Science-Introduction to Video and Image Processing, Thomas B. Moeslund, 2012, Springer-Verlag London

http://what-when-how.com/introduction-to-video-and-image-processing/blob-analysis-introduction-to-video-and-image-processing-part-1/

http://www.roborealm.com/ http://sine.ni.com/nips/cds/view/p/lang/en/nid/2881 http://www.cognex.com/machine-vision-applications.aspx