How to select a region if we click inside it?

Question

Meshooo 2014-1-8

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https://ww2.mathworks.cn/matlabcentral/answers/111734-how-to-select-a-region-if-we-click-inside-it

评论： Image Analyst 2016-10-24

Dear all,

I have a binary image same as the one I show here which contains few honeycomb regions connected to each other. Now I want a single honeycomb to be selected when the user makes a left click using the mouse inside the desired honeycomb. Any idea how

to do that?

Any suggestions will be appreciated.

Sincerely, Mueshoo

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Answer 1

Matt J 2014-1-8

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Use WAITFORBUTTONPRESS and get(gca,'CurrentPoint') to detect the location of the click.

Then use INPOLYGON to detect which honeycomb was selected.

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Matt J 2014-1-14

在 MATLAB Online 中打开

For example the rows of V

V=[0 0 ; 1 0; 0 1]

are vertices of a triangle.

Since (0.1,0.2) lies inside the triangle, this returns true

 >>inpolygon(0.1,0.2,V(:,1),V(:,2))
ans =
       1

and conversely this returns false,

>> inpolygon(.1,1.2,V(:,1),V(:,2))
ans =
       0

Meshooo 2014-1-15

regular_shapes.png

Thank you but still I couldn't do it. Let's say we have many objects in one image as I show here. Now if the user click by the mouse inside any object then this object will remain and all other objects will be removed. Is it possible to do that? Thank you very much for your time.

Mustafa

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Answer 2

Image Analyst 2014-1-15

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Mustafa: Here's how to do it step by step:

invert the image
call imclearborder
label the binary image with bwlabel
call [column, row] = int32(ginput(1)) to let the user click somewhere
get the label with labelNumber = labeledImage(row, column)
extract the object with extractedObject = ismember(labeledImage, labelNumber)
Make it binary again binaryImage = extractedObject > 0;
display it with imshow(binaryImage, []);

See if you can program that up and attach your code if you have problems.

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Meshooo 2014-1-15

在 MATLAB Online 中打开

Thank you very much. I tried to solve it in a similar way and now it works perfectly. However, it is now working for my sample image that contain 6 objects as shown in the attached image. Do you know how to make a loop such that it can work for any number of objects in the image?

Please check my code

I = imread('regular_shapes.tif');
%
BW = im2bw(I);
%
b = bwboundaries(BW);
%
bb1 = b{1};   %x, y of the first object
bb2 = b{2};   %x, y of the 2nd object
bb3 = b{3};   %x, y of the 3rd object
bb4 = b{4};   %x, y of the 4th object
bb5 = b{5};   %x, y of the 5th object
bb6 = b{6};   %x, y of the 6th object
%
X_obj1 = bb1(:, 1);
Y_obj1 = bb1(:, 2);
X_obj2 = bb2(:, 1);
Y_obj2 = bb2(:, 2);
X_obj3 = bb3(:, 1);
Y_obj3 = bb3(:, 2);
X_obj4 = bb4(:, 1);
Y_obj4 = bb4(:, 2);
X_obj5 = bb5(:, 1);
Y_obj5 = bb5(:, 2);
X_obj6 = bb6(:, 1);
Y_obj6 = bb6(:, 2);
%
figure, imshow(BW);
hold on
[yCenter, xCenter] = ginput(1)
hold off
%
Selec_1 = inpolygon(xCenter,yCenter,X_obj1,Y_obj1);
Selec_2 = inpolygon(xCenter,yCenter,X_obj2,Y_obj2);
Selec_3 = inpolygon(xCenter,yCenter,X_obj3,Y_obj3);
Selec_4 = inpolygon(xCenter,yCenter,X_obj4,Y_obj4);
Selec_5 = inpolygon(xCenter,yCenter,X_obj5,Y_obj5);
Selec_6 = inpolygon(xCenter,yCenter,X_obj6,Y_obj6);
%
[L, num_Obj] = bwlabel(BW, 4);
Obj_1 = L ==1;
Obj_2 = L ==2;
Obj_3 = L ==3;
Obj_4 = L ==4;
Obj_5 = L ==5;
Obj_6 = L ==6;
%
if Selec_1 == 1
    Obj = L ==1;
elseif Selec_2 == 1
    Obj = L ==2;
    elseif Selec_3 == 1
    Obj = L ==3;
    elseif Selec_4 == 1
    Obj = L ==4;
    elseif Selec_5 == 1
    Obj = L ==5;
    elseif Selec_6 == 1
    Obj = L ==6;
end
%
figure, imshow(Obj);

YEIMY LISETH QUINTANA VILLAMIZAR 2016-10-23

Can you help me? please,

I need that the program recognize a image of another image, loading a image that is a circle and loading other that is a ellipse.

How I can make that the program recognize that the image is a circle or a ellipse ?

Image Analyst 2016-10-24

shape_recognition_demo.m

See my shape recognition demo, attached.

Also see this paper: https://www.ecse.rpi.edu/homepages/qji/Papers/ellipse_det_icpr02.pdf

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How to select a region if we click inside it?

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