Perimeter and area of the Circle

Hello..:) my problem is to get the perimeter and area of the circle.. here is my binary image..

i still new with matlab..any very greatful for those who are helping me please help me by giving ur idea or suggestion for the coding..thx for ur time..:)

Answer 1

[Image Analyst]

The steps:

1. Crop out just the middle of the image to get rid of the straight lines.
2. Call labeledImage = bwlabel(binaryImage)
3. Call regionprops(labeledImage, 'PixelList') to get the (x,y) coordinates of each ring.
4. For each ring, fit the coordinates to a circle with the FAQ

Let me know if you still need help after this. If so, attach your code.

[ahmad aizat]

thx for ur answer sir..but im still stuck at point 3 to get the xy coordinate..

hope u can giv me the detail...

A=imread('hitam(5).jpg');

Z=im2bw(A);

labeledImage = bwlabel(Z);

stats=regionprops(labeledImage, 'PixelList');

am i doing it right? can i get the perimeter value automatically?

[Image Analyst]

ahmad, the problem is that you don't have a good binary image to start with. Your rings are broken up into many many separate blobs:

You need to do a better job of getting the rings. It's possible to "fix up" this image but it would be so much better if you just got a good image to begin with.

Here is the code I used:

% Demo to try to find rings.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 14;

%===============================================================================
% Read in a standard MATLAB gray scale demo image.
folder = 'D:\temporary stuff';
baseFileName = 'Hitam(5)edge.jpg';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorBands] = size(grayImage);
if numberOfColorBands > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage, []);
axis on;
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 

% Crop off unneded stuff
grayImage = grayImage(100:420, 240:560);

% Create a binary image
binaryImage = grayImage > 127;
% Display the binary image.
subplot(2, 2, 2);
imshow(binaryImage, []);
title('Binary Image', 'FontSize', fontSize);

% Label each blob with 8-connectivity, so we can make measurements of it
[labeledImage, numberOfBlobs] = bwlabel(binaryImage, 8);
% Apply a variety of pseudo-colors to the regions.
coloredLabelsImage = label2rgb (labeledImage, 'hsv', 'k', 'shuffle'); 
% Display the pseudo-colored image.
subplot(2, 2, 3);
imshow(coloredLabelsImage);
caption = sprintf('%d Individual Blobs', numberOfBlobs);
title(caption, 'FontSize', fontSize);
fprintf('Found %d blobs.\n', numberOfBlobs);

% Measure the areas and coordinates.
measurements = regionprops(labeledImage, 'Area', 'PixelList');
% Get all the areas from a structure into a single array.
allAreas = [measurements.Area]

helpdlg('Done with demo.  Look in command window for areas.');

[ahmad aizat]

thx a lot with ur help sir..now i can start converting the pixel value to mm unit..:)

[Image Analyst]

You just need to multiply by a calibration scale factor. See my attached spatial calibration demo.

[ahmad aizat]

Sir..i have study about the spatial calibration demo but do i need to draw the line manually? i still confuse on how to convert it sir..please help me..:(

For your information..the distance of the camera to the object is 300mm and the picture size is 640x480.