Profile of image in grey scales

Good afternoon, I would really appreciate if you could help me with a particular issue related with image analysis. I have a set of images in grey scales. From the images I require to get an edge of the profile. I have tried different commands to get the profile or edge of the flow. Using canny and imerode and imdilate commands the best that I got is as shown in the image. However I need to get an edge of the whole profile as with the red line in image attached.

Any suggestions

Thanks a lot in advance

Best regards,

The script for this part is:

threshold = graythresh(MyImage); bw = im2bw(MyImage,threshold); se = strel('disk',2); bw = imclose(bw,se); BWsdil = imdilate(bw, se); BWsdil = bwperim(BWsdil); BWoutline=edge(BWsdil, 'canny',0,1);

Segout = MyImage; Segout(BWoutline) = 255;

figure(1), imshow(Segout)

Answer 1

[Image Analyst]

You don't need edge detection at all. Just threshold and go along column by column using find() to find the top row. Something like (untested)

binaryImage = grayImage > 50; % Adjust the value to eliminate dark background.
binaryImage  = bwareaopen(binaryImage, 200); % Get rid of blobs smaller than 200
imshow(binaryImage);
[rows columns] = size(binaryImage);
topRows = rows * ones(rows, columns, 'int32'); % Initialize
for col = 1 : columns
  topRows(col) = find(binaryImage(:, col), 1, 'first');
end

[Image Analyst]

Referring to your "Answer" below (which should have been a comment here)...

Why do you have 3 blobs? Aren't you after the top most surface? If you want them as three separate blobs, then just use

boundaries = bwboundaries(binaryImage);

And you should not lose all your data by getting rid of blobs smaller than 200 pixels.

Please post the original grayscale image with no canny and no red outlines.

[600Seat]

Sorry, I didn't know where to write my answer to you. Thanks for letting me know. My intention is to get the whole flow with a perfect BLACK background. What I was trying to get is the profile or edge of the whole profile. With that edge I can apply that everything outside the flow to be black (i.e. '0') and everything inside the flow to keep the original image. In this way, I get a perfect black background and I dont loose any information inside the flow. Some of the balls go faster and they separate from the whole flow. They are very important too. However, I think blobs smaller than 200 pixels should be fine. I have tried using boundaries = bwboundaries(binaryImage); However I get similar results than with my scripts. I dont get a outline line as I need it. Thanks a lot for your support. I really appreciate it.

<http://i.imgbox.com/aczjxmcl.jpg> <http://i.imgbox.com/adixQ4Yr.jpg>

[600Seat]

[600Seat]

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Answer 2

[600Seat]

Thanks for your reply. I have tried your suggestion. However I am not getting an edge similar to the red line edge as showed in my previous image.

I have tried using different values to eliminate dark background. Since with 50, I eliminate the background and mainly all the data that I need.

The second command to get rid ob blobs smaller than 200, I cannot used since again I loose all my data.

I am looking for some command to join the gaps between the white groups. It should be something as a curve with best fit. But I am not sure how to do it.

It could be that I am trying to do something that it is not possible... I dont know.

I would appreciate it if you could help me with this. Thanks