Draw rectangular contour in thresholded image

2018 3 20
1 个回答
更新时间：2018 4 4
5 次查看（30 天）

0 个投票

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

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回答（1 个）

Image Analyst
Image Analyst 2018-3-20

0 个投票

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.

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Nachiket Patki
Nachiket Patki 2018-3-21
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
Image Analyst 2018-3-21
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
Nachiket Patki 2018-3-21
Sir, can you tell me what is that 'textline'? It's giving me an error saying textline is undefined
Image Analyst
Image Analyst 2018-3-22
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
Nachiket Patki 2018-3-25
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
Image Analyst 2018-3-25
编辑：Image Analyst 2018-3-25
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
Nachiket Patki 2018-4-4
Ohh I just missed that... Again thank you very much, sir. Your answers have always helped me.

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