Select a ROI (circle and square) in matlab in order to aply a filter

Question

I am working on matlab and I want to do an interactive selection like you do when you use the function roipoly, but I want to select or a circle or a square. I already search for funcion to select a region of interest (ROI) like you select when you use roipoly but using a circle or a square but I can't find anything.

Any tips?

I already tried using the ginput.

[X, Y]= ginput(2)

xmin=min(X)
xmax=max(X)
ymin=min(Y)
ymax=max(Y)

In this code I define the corner of the square (the user defines the two points with the ginput). But when I check the points of the image, they are wrong. I think is because of the size of the figure that is not the same on the plot.

The best way to select the ROI that I want is to using a function similar with the roipoly, but for a circle and for a square, instead of a polygon. And with this type of function I have only can select points inside of the picture with the "ginput" I have to type a error message if the user select any point outside of the figure (the problem is that they don't match, the point that I can select is greater then the size of the image).

Answer 1

There are really two questions here:

1) What is wrong with your GINPUT code and 2) How to write roiCircle or roiSquare

In answer to (1), nothing is wrong; that code behaves as it should:

imgData = randn(100);
imagesc(imgData );
[X, Y]= ginput(2)

xmin=min(X);
xmax=max(X);
ymin=min(Y);
ymax=max(Y);

squareX = [xmin xmin xmax xmax xmin];
squareY = [ymin ymax ymax ymin ymin];
hold on; 
plot(squareX,squareY); %plot the correct square
hold off;

You can use IMCROP to get the data:

width = xmax - xmin;
height = ymax - ymin;
imgSelect = imcrop(imgData,[xmin,ymin,width,height]);
figure; imagesc(imgSelect);

As far as (2) (writing roiCircle or roiSquare), so that they update nicely like roiPoly does, those will require a significant (though not insurmountable) amount of MATLAB GUI programming. It's tractable, but not trivial.