I want to reuse ROI selected by imellipse from an image

I have an image with various ROI selected using imellipse. I do some color processing within those ROI, and output a new image. I want to select the ROI only once throughout the lifetime of an image. In other words, keep the exact same ROI, but change some parameters and output another image at later date (or perhaps let another user do the same analysis with different parameter, but same ROI).

How can I store / reproduce / redraw the ellipse ROIs resulting from imellipse? The only thing I can think of is to store result of createMask as another image. Is there another way to do this? My images are large, and ideally I don't want to store the whole image mask. All my ROIs combined... end up being less than 10-11% of the original image. Storing 90% of the non-interesting ROI data seems like a waste.

Any ideas?

Answer 1

[Image Analyst]

With code like this:

userPrompt = sprintf(' Click and drag out an ellipse.\nDouble click inside of it to accept it.');
uiwait(msgbox(userPrompt));
hEllipse = imellipse(gca); % Second argument defines ellipse shape and position.
% Wait for user to finalize the size and location.
xyCoordinates = wait(hEllipse)

I think you could just save hEllipse or xyCoordinates to a .mat file and that would take up a lot less space than the mask image.

[Divya]

I looked into the coordinates option, but I didn't see a way to use those coordinates to redraw the whole ellipse. The ellipse itself doesn't seem to be created by straight-line connections between those points. Also, saving matrix is an option, but that's basically storing the resulting binary image from createMask. I can check if that .mat of that data is more frugal than saving the binary image. Thanks for that recommendation.

[Image Analyst]

Divya, you use poly2mask() to redraw the whole ellipse as a mask. You can save the coordinates:

save(filename, 'xyCoordinates');

Then recall them

storedStructure = load(filename);
xyCoordinates = storedStructure.xyCoordinates;

Then reconstruct your binary mask image

[rows, columns, numberOfColorChannels] = size(yourImage);
binaryImage = poly2mask(xyCoordinates(:,1), xyCoordinates(:,2), rows, columns);

[Syeda Noor]

How to create a binary mask of colored image of circular shape. For segmentation purpose.

[Image Analyst]

Syeda, probably by thresholding. After you use the Color Thresholder on the Apps tab, post your code and image in a new question if you have any trouble.