Creating a ROI numerically (without clicking) with impoly

Hello, i do have some points (which i know the coordinates) of a greyscale image and i used them to generate a polygon (using boundary function since they are not connected in some regions) so i have an area closed.

Now i want to extract all the info thats outside that region, (everything inside 1, outside 0) so i have a binary image.

I guess the easiest form is to generate a ROI and create a mask trough that ROI, but I see no way to do it automatically ( I dont want to click on the points of my poligon, its not an accurate procedure and it takes too much time).

Anyone has any idea of how to proceed?

Thanks

Answer 1

[Subhadeep Koley]

I am assuming you are trying to create Polygonal ROI Non-interactively. The code below might help!

% Read the image into the workspace
I = imread('cameraman.tif');
% Display the image
imshow(I, []);
% Draw a Point ROI on the image with specified points
roi = images.roi.Polygon(gca, 'Position', [115 30; 80 45; 80 80; 115 90; 145 65]);

[JoaquinB]

Hello, what about if i have a really big number of points?

Can i....

roi = images.roi.Polygon(gca, 'Position', [PIX_pos]);

Where Pix_pos is an array (1000x2) for example:

X Y

200 300

400 600

etc etc

or do i need to automatise it like:

roi = images.roi.Polygon(gca, 'Position', [PIX_pos(1,1) PIX_pos(1,2);PIX_pos(2,1) PIX_pos(2,2); etc etc;]);

Thanks

[Subhadeep Koley]

You can specify point values like below also.

% Read the image into the workspace
I = imread('cameraman.tif');
% Display the image
imshow(I, []);
% Specify the points
pointVals = [115 30; 80 45; 80 80; 115 90; 145 65]; % Here "pointVals" is a (5x2) vector
% Draw a Point ROI on the image with specified points
roi = images.roi.Polygon(gca, 'Position', pointVals);

Hope this helps!

[JoaquinB]

Yea, that was obvious, forgot the Matlab notation.

Thanks a lot Subhadeep!

[Subhadeep Koley]

No problem!