Draw rectangular contour in thresholded image

Hello, I have a thresholded image of a bottle, where the liquid color is being masked and thresholded.

Now I want to find the height of that liquid present inside the bottle. What I am thinking is I will find the rectangular contour covering the liquid inside the bottle...and the height of the rectangle will give me a height of liquid. So how to draw react contour is the first question or is there any better way of finding height of liquid present?

Thank you

Answer 1

[Image Analyst]

What you are saying is this:

binaryImage = bwareafilt(binaryImage, 1); % Extract largest blob only.
props = regionprops(binaryImage, 'BoundingBox');
height = props.BoundingBox(4)

This way is susceptible to little outliers, like the two you have on the top. A better way may be to either scan the blob vertically getting the height at every column and then taking the average

heights = zeros(rows, 1);
for col = 1 : columns
    thisColumn = binaryImage(:, col);
    if max(thisColumn) > 0  % If there are white pixels in the column
        topRow = find(thisColumn, 1, 'first');
        bottomRow = find(thisColumn, 1, 'last');
        heights(col) = bottomRow - topRow + 1;
    end
end
averageHeight = mean(heights(heights>0))

Or, get the average vertical profile and threshold it at some level

verticalProfile = sum(binaryImage, 2);
averageHeight = sum(verticalProfile > someLevel)

All 3 methods will/could give different heights. It just depends on how you want to define height. I mean, look at the bottom of your bottle - it's not flat so you don't have a perfect rectangle aligned with the edges of the image, so there are different ways to define height.

[Nachiket Patki]

Thank you very much sir. Sir I have another task where I have a text file which contains information in three rows like this...

Name1 5 EC 256 ACPCE

Name2 5 EC 253 ACPCE

Name2 15 EC 255 ACPCE

these three line. If X contdition occurs I want to access first line(access and store string in variable), if Y occurs second and if none then third, how can do this?

[Image Analyst]

Try this:

% Open the file.
fileID = fopen(fullFileName, 'rt');
if fileID ~= -1
  % If file could be opened...
  % Skip the proper number of lines.
  if X
    linesToSkip = 0;
  elseif Y
    linesToSkip = 1;
  else
    linesToSkip = 2;
  end
  for k = 1 : linesToSkip
    % Read and throw away lines of the file.
    fprintf('Skipping Line #%d: %s\n', linesToSkip+1, textLine);
    % Read the next line.
    textLine = fgetl(fileID);
  end
  fprintf('Reading Line #%d: %s\n', linesToSkip+1, textLine);
  % Read the next line of the file.
  textLine = fgetl(fileID);
  % All done reading all lines, so close the file.
  fclose(fileID);
else
  errorMessage = sprintf('Error opening %s', fullFileName);
  uiwait(errordlg(errorMessage));
end

[Nachiket Patki]

Sir, can you tell me what is that 'textline'? It's giving me an error saying textline is undefined

[Image Analyst]

Try this:

% Open the file.
fileID = fopen(fullFileName, 'rt');
if fileID ~= -1
  % If file could be opened...
  % Skip the proper number of lines.
  if X
    linesToSkip = 0;
  elseif Y
    linesToSkip = 1;
  else
    linesToSkip = 2;
  end
  for k = 1 : linesToSkip
    % Read and throw away lines of the file.
    fprintf('Skipping Line #%d: %s\n', linesToSkip+1, textLine);
    % Read the next line.
    textLine = fgetl(fileID);
  end
  % Read the next line of the file.
  textLine = fgetl(fileID);
  fprintf('Read Line #%d: %s\n', linesToSkip+1, textLine);
  % All done reading all lines, so close the file.
  fclose(fileID);
else
  errorMessage = sprintf('Error opening %s', fullFileName);
  uiwait(errordlg(errorMessage));
end

[Nachiket Patki]

Thank you very much sir. This was one part of the project. The second part is I want to save info into text file (in the same format above) which will be supplied from the GUI. In simple words I want to do exactly the reverse of this what we are trying to do now. The same info has to be entered into text via inputs from GUI. So I use...

n=(get(handles.edit1,'string'));

r=(get(handles.edit2,'string'));

b=(get(handles.edit3,'string'));

y=(get(handles.edit4,'string'));

fprintf(fileID,'%s %s %s %s\n',n,r,b,y);

It's not working I am getting an error... where am I going wrong?

[Image Analyst]

If you're going to write out four strings, you'll need four %s in the format specifier string.

n = handles.edit1.String;
r = handles.edit2.String;
b = handles.edit3.String;
y = handles.edit4.String;
outputFileID = fopen(fullOutputFileName, 'wt');
fprintf(outputFileID, '%s %s %s %s %s\n', n, r, b, y);
fclose(outputFileID);

[Nachiket Patki]

Ohh I just missed that... Again thank you very much, sir. Your answers have always helped me.