Dienstag, 23. April 2013

TABLE TENNIS BALL DETECTION-MATLAB CODE:


Using the concept of roundness to detect a circular object, the table tennis ball in mid air or in palm is detected.

FLOW CHART:


1.     Read input image
·        Read a RGB image with ball in mid air or ball in palm.
                   MATLAB CODE:
                       %Read the input image
         Img=imread(Filename);
         axes('Position',[0 .1 .74 .8],'xtick',[],'ytick',[]);
         imshow(Img);title('Original Image');




2.     Image Pre-processing
·        Convert the RGB image to grayscale image.
·        Apply median filter
·        Adjust the brightness and contrast of the image using ‘imadjust’ function.
                      MATLAB CODE:
           I=rgb2gray(Img);     % Converting RGB Image to
                                % Gray Scale Image
           I=im2double(I);      % Converting Gray scale Image
                                % to Double type

           J = medfilt2(I,[3 3]); % Median Filter , 
                                  % 3x3 Convolution
                                  % on Image
           I2 = imadjust(J);     % Improve to quality of Image
                                 % and adjusting
                                 % contrast and brightness values




3.     Threshold the image
·        The pixel value greater than the threshold value is converted to one else zero.
                     MATLAB CODE:
           Ib = I2> 0.9627; 









4.     Image Labeling
·        Label the connected components using ‘bwlabel’ function
·        Remove components that are smaller in size.
                     MATLAB CODE:
           %Labelling
           [Label,total] = bwlabel(Ib,4); % Indexing segments by
                                          % binary label function

            %Remove components that is small and tiny
            for i=1:total
                if(sum(sum(Label==i)) < 500 )

                    Label(Label==i)=0;
  
                end
            end


5.     Find the image properties: Area, Perimeter and Centroid
·        Using ‘regionprops’ function, find the Area, Perimeter, Bounding Box and Centroid.
                     MATLAB CODE:
            %Find the properties of the image
             Sdata = regionprops(Label,'all'); 

6.     Calculate the Roundness
·        Roundness = 4*PI*A/P^2
           MATLAB CODE:
                %Find the components number
          Un=unique(Label);
          my_max=0.0;

            %Check the Roundness metrics
            %Roundness=4*PI*Area/Perimeter.^2
            for i=2:numel(Un)
               Roundness=(4*pi*Sdata(Un(i)).Area)/Sdata(Un(i)).Perimeter.^2;
               my_max=max(my_max,Roundness);
                if(Roundness==my_max)
                   ele=Un(i);
                end
            end

7.     Find the component with the maximum roundness value
·        Find the max of the Roundness value for all the labeled components
8.     Show the detected table tennis ball
·        Use the ‘BoundingBox’ values to plot rectangle around the ball
·        Mark the centroid of the ball
                     MATLAB CODE:
          %Draw the box around the ball
           box=Sdata(ele).BoundingBox;
           box(1,1:2)=box(1,1:2)-15;
           box(1,3:4)=box(1,3)+25;

          %Crop the image
           C=imcrop(Img,box);

          %Find the centroid
          cen=Sdata(ele).Centroid;


          %Display the image

           axes('Position',[0 .1 .74 .8],'xtick',[],'ytick',[])
           imshow(Img);
           hold on
           plot(cen(1,1),cen(1,2),'rx');%Mark the centroid




9.     Generate report
·        Find the radius using the Equidiameter obtained using ‘regionprops’ function.
·        Display the radius,Area,Perimeter and Centroid of the ball.
·        Show the Binary and Original image of the cropped ball.
MATLAB CODE:

        Rad=(sdata(ele).EquivDiameter)/2;
        Rad=strcat('Radius of the Ball :',num2str(Rad));
     
        Area=sdata(ele).Area;
        Area=strcat('Area of the ball:',num2str(Area));
       
        Pmt=sdata(ele).Perimeter;
        Pmt=strcat('Perimeter of the ball:',num2str(Pmt));
       
        Cen=sdata(ele).Centroid;
        Cent=strcat('Centroid:',num2str(Cen(1,1)),',',num2str(Cen(1,2)));






BALL IN MID AIR:





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