Shape detection in image

Hello, I have an image with many shapes and I need to write some Matlab code which remove all the shapes except the rectangle.. Does it availabe to do it using only with strel,imclose and bwareaopen? if you think yes i will be very happy to hear your opinion.

Thanks a lot!

The Image:

Answer 1

[Image Analyst]

Try this code:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 20;

% Open an image.
% Browse for the image file. 
[baseFileName, folder] = uigetfile('*.*', 'Specify an image file'); 
fullImageFileName = fullfile(folder, baseFileName); 
if folder == 0
  return;
end

% Read in image into an array.
[rgbImage, storedColorMap] = imread(fullImageFileName); 
[rows, columns, numberOfColorBands] = size(rgbImage)
% If it's monochrome (indexed), convert it to color. 
% Check to see if it's an 8-bit image needed later for scaling).
if strcmpi(class(rgbImage), 'uint8')
  % Flag for 256 gray levels.
  eightBit = true;
else
  eightBit = false;
end
if numberOfColorBands == 1
  if isempty(storedColorMap)
    % Just a simple gray level image, not indexed with a stored color map.
    % Create a 3D true color image where we copy the monochrome image into all 3 (R, G, & B) color planes.
    rgbImage = cat(3, rgbImage, rgbImage, rgbImage);
  else
    % It's an indexed image.
    rgbImage = ind2rgb(rgbImage, storedColorMap);
    % ind2rgb() will convert it to double and normalize it to the range 0-1.
    % Convert back to uint8 in the range 0-255, if needed.
    if eightBit
      rgbImage = uint8(255 * rgbImage);
    end
  end
end 

% Display the original image.
subplot(2, 2, 1);
imshow(rgbImage);
set(gcf, 'Position', get(0,'Screensize')); % Enlarge figure to full screen.
set(gcf,'name','Image Analysis Demo','numbertitle','off') 
drawnow; % Make it display immediately. 
if numberOfColorBands > 1 
  title('Original Color Image', 'FontSize', fontSize); 
  grayImage = rgbImage(:,:,1);
else 
  caption = sprintf('Original Indexed Image\n(converted to true color with its stored colormap)');
  title(caption, 'FontSize', fontSize);
  grayImage = rgbImage;
end
% Display it.
subplot(2, 2, 2);
imshow(grayImage, []);
title('Grayscale Image', 'FontSize', fontSize);

% Binarize the image.
binaryImage = grayImage < 100;
% Display it.
subplot(2, 2, 3);
imshow(binaryImage, []);
title('Binary Image', 'FontSize', fontSize);

% Remove small objects.
binaryImage = bwareaopen(binaryImage, 300);
% Display it.
subplot(2, 2, 4);
imshow(binaryImage, []);
title('Cleaned Binary Image', 'FontSize', fontSize);

[labeledImage numberOfObjcts] = bwlabel(binaryImage);
blobMeasurements = regionprops(labeledImage,'Perimeter','Area', 'Centroid'); 

% for square ((a>17) && (a<20))
% for circle ((a>13) && (a<17))
% for triangle ((a>20) && (a<30))
circularities = [blobMeasurements.Perimeter].^2 ./ (4 * pi * [blobMeasurements.Area])
hold on;

% Say what they are
for blobNumber = 1 : numberOfObjcts
  if circularities(blobNumber) < 1.19
    message = sprintf('The circularity of object #%d is %.3f, so the object is a circle',...
      blobNumber, circularities(blobNumber));
    theLabel = 'Circle';
  elseif circularities(blobNumber) < 1.53
    message = sprintf('The circularity of object #%d is %.3f, so the object is a Rectangle',...
      blobNumber, circularities(blobNumber));
    theLabel = 'Rectangle';
  else
    message = sprintf('The circularity of object #%d is %.3f, so the object is a triangle',...
      blobNumber, circularities(blobNumber));
    theLabel = 'Triangle';
  end
  text(blobMeasurements(blobNumber).Centroid(1), blobMeasurements(blobNumber).Centroid(2),...
    theLabel, 'Color', 'r');
  uiwait(msgbox(message));
end

[Alejandro Bastidas]

Excellent code !!!!!

[Syukri Yazed]

With small adjustment on the reading image part:

% Open, Read, & Display Image
baseFileName = 'F:\PhD\MATLAB CODING\BlobsDemo\shape.png';
rgbImg = imread(baseFileName);
[rows, columns, numberOfColorBands] = size(rgbImg);
subplot(2, 2, 1);
imshow(rgbImg);
set(gcf, 'Position', get(0,'Screensize')); % Enlarge figure to full screen.
set(gcf,'name','Image Analysis Demo','numbertitle','off') 
drawnow; % Make it display immediately.

Success.

Although there is 75% detected correctly, 25% wrong detection occur.

@Image Analyst.. Can you suggest me regarding this matter, on how can the code detect a square shape correctly..

[Image Analyst]

@Syukri Yazed, for a square, you can call regionprops and look at the bounding box. If it's a perfect square the width and height will be the same

labeledImage = bwlabel(binaryImage);
% Measure the bounding boxes.
props = regionprops(binaryImage, 'BoundingBox');
allBB = vertcat(props.BoundingBox);
allWidths = allBB(:, 3)
allHeights = allBB(:, 4)
% Determine which blobs are square or not.
isASquare = allWidths == allHeights
% Extract the squares
squaresOnlyImage = ismember(labeledImage, find(isASquare));
imshow(squaresOnlyImage);

[Syukri Yazed]

@Image Analyst,

I've got 2 results the first result was not successful, the second result was a success; but with difference images.

Here I attach my code with the images and the results.

Could you please look into this..

Thank you.

[Beenish Ishtiaq]

@Image AnalystThis code is detetcting all images as triangle.Kindly give the code detetcting all the basic shapes correctly in every image.

[Beenish Ishtiaq]

Also kindly share the code that counts each shape in the given image