MATLAB image interactive operation, the mouse selects an area of the image

Sometimes we need to take out part of the image , And it may be different every time , Using code to get some trouble , It is better to draw this area with the mouse , And take it out .

matlab It comes with some functions for interactive image operation , Record it here ;

1. getpt
   effect ： You click a pixel of the image with the mouse , Return the position of this pixel
   usage ：[x,y] = getpts
   Example ：

img = imread('lena.jpg');
figure;imshow(img)
[x,y] = getpts; %x Is listed ,y Yes 

2. getrect
   effect ： Select a rectangular area
   usage ：p= getpts;p Four numbers returned , The columns of pixels in the upper left corner are in turn , Row of pixels in the upper left corner , Column length , governor , From these four values, we can determine a rectangular area .
   Example ：

img = imread('lena.jpg');
imshow(img)
p = getrect;  % Return area location information 
p = round(p); 
I = img(p(2):p(2)+p(4),p(1):p(1)+p(3));  % Index image 

3. imcrop
   effect ： Select a rectangular area , Follow getrect almost
   usage ：I = imcrop(img); Return value I Is the sub image you selected , It's no longer a regional location .
   Example ：

img = imread('lena.jpg');
% imshow(img)
I = imcrop(img);  % Return area location information 

The above is the method of taking points and rectangular boxes , The above functions can already meet a large part of the requirements , Sometimes you may need to extract other shapes ,matlab There are many ways to intercept images , I'll sort it out , If you have needs, you can click the link .

If you use the functions in the table , Pay attention to one problem , We usually extract an image , Not just to draw , Maybe it's more about the value in the sub image , But the functions in the table do not directly take out the value , Here I am inROI Function traverses the original image , Specific examples ：

path = 'lena.jpg';
img = double(imread(path));
imshow(img/255)
h = drawpolygon   % Extract polygon sub image 
data = [];
for i = 1:size(img,1)
   for j = 1:size(img,2)
       img_tar(i,j) = inROI(h,j,i);  %ROI  Binary image 
       if img_tar(i,j)==1
          data = [data img(i,j)];    %ROI The data in 
       end
   end
end
figure;imshow(img_tar)