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Source code:  coinHunt.m, findLocMax.m, drawCircle.m, colorCoins.m.
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Summary:

This program uses Houph Transform to detect coins in the image.  Originally it used to search 20 radii in order to find the coins.  Unfortunately, that approach caused the program to run for a very long time (due to the nature of Matlab software package).  So, I determined the radii of each coin in the picture, and give the radius of the coin as an input parameter.  The use of only one radius reduced the Houph Transform computation (coinHunt.m) time to about a minute. Also, I broke the program into two parts: Hough Transform computation, and detecting the position of coins by evaluating matrix, generated by coinHunt.m. This matrix holds the "voting" information for each pixel. This second part of the program is called findLocMax.m, which stands for Find Local Maximum.
 

•  coinHunt -- the main driver of the program: performs the Houph transform and saves the voting information in the 'matrix.mat' file to pass input information to findLocMax.m.  This step helps to avoid re-running the coinHunt method over and over again during the development stage.

 
•  findLocMax -- detects the local maxima in  Houph transform array and draws the circles around the detected coins.

 
•  drawCircle: draws a circle around the passed in center information. The radius of the circle is specified by the user and is passed in to the coinHunt method.

 
•  ColorCoins: draws a circle around the detected coins in the original image.

Output:

The following pictures were outputted by my program. The program was run twice: first, to detect quarters, and after that, on the produced result to detect cents.

Hough Transform for quarters	Hough Transform for cents

Here, the output from the Houph Accumulator array, are scaled by the highest vote for the center of the pixel.

Original Image	Detected Coins

As you can see the program found all of the coins: there is a thin line around all of the quarters.

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If you have any questions please e-mail me at:  shleyf@cc.gatech.edu