Active Contour run time warning

Why I get a warning while using active contour in MATLAB?

Warning: Iterations terminated prematurely because no part of the contour lies within the image domain. If the range of pixel values in the input image is small (such as 0-1)

[Adam Danz]

The warning tells you why it's appearing. We cannot explain why this is happening without more info such as the image, inputs to activecontour, etc.

[Tamoor Aziz]

Thank you so much for your answer. I am using the following code,

{

mask = logical(Image);
 bw = activecontour(Image,mask,500,'Edge','SmoothFactor',1.5);

}

The contour method cannot converge towards the edge of the dark object beacuse of premature termination of the iterations.

[Adam Danz]

What is "Image"? I see that there's an attachment named Image.png and I assume the variable Image stores the image data of that file but how are you reading it in?

Since you're applying logical() I assume the image data are binary.

[Tamoor Aziz]

Thank you so much for your prompt reply and apology for my mistake.

The mask is the bounding box of the dark object and is logical. I want to segment the dark object using active contour segmentation. It works, but due to premature termination of iteration, it can't converge to the object exactly.

mask = logical(BoundingBox);

bw = activecontour(Image,mask,500,'Edge','SmoothFactor',1.5);

[Image Analyst]

Exactly? Do you mean that there is an exact solution? Where exactly is the border of that blurry smooth shape? Can you indicate it in a red curve? It looks like a judgment call to me. What about simply thresholding and calling bwboundary()?

boundary = bwboundaries(grayImage < someGrayLevel);

[Adam Danz]

Now I have the same question for "BoundingBox". What is it? I understand it was created using mask.png and that it's probably a binary matrix but we can't be sure without having the line of code you used to read in that file and create 'BoundingBox'.

[Image Analyst]

The mask is some initial shape for the activecontour() function. See my attached demo.

[Adam Danz]

You've always got great demos, Image Analyst.

I'd like the OP to share how BoundinBox was created to eliminate that step as a possible cause of the problem and to ensure that we're identically replicating the problem. That would only be 2-3 lines from your demo,

grayImage = imread(fullFileName);
mask = grayImage > thresholdValue;

And for the composite mask,

mask = bwconvhull(mask, 'Union');

Answer 1

[Tamoor Aziz]

@Image Analyst, thank you so much for your reply. Exactly, My problem is the same as you described in https://www.mathworks.com/matlabcentral/answers/705903-active-contour-run-time-warning#comment_1240593.

According to my understanding, if you increase the number of iteration then you will get the accurate final outer boundary of the object in the "Original Grayscale Image".

But, I don't have problem about the contour segmentation. Please help me with my problem. If I use 400 number of iterations, the contour segmentation process stops before than 400 iterations and it generates the warning! Why I get a warning while using active contour in MATLAB?

Warning: Iterations terminated prematurely because no part of the contour lies within the image domain. If the range of pixel values in the input image is small (such as 0-1)