Matlab: how to save the image result Real-time plotting of ROI selected with IMRECT

Question

I am confused about how to save the ROI resulting from calling imrect. I want to save the image on subplot(2,1,2)

The code is:

function Zoomer
figure();

highResImage = imread('E:\My Work\THESISQ\FIX\Koding\data coba\Image_3060.jpg');
lowResImage = imresize(highResImage,0.5);

a1 = subplot(2,1,1);
a2 = subplot(2,1,2);

imshow(lowResImage,'Parent',a1);
initialPosition = [10 10 100 100];
lowResRect = imrect(a1,initialPosition);

lowResRect.addNewPositionCallback( @(pos)Callback(pos,a2,highResImage));

Callback( initialPosition , a2, highResImage);
end

function Callback(position,axesHandle, highResImage)
position = position * 2;
x1 = position(1);
y1 = position(2);
x2 = position(1) + position(3);
y2 = position(2) + position(4);

highResThumbnail = highResImage( round(y1:y2),round(x1:x2),:);

if isempty( get(axesHandle,'Children')) 
    imshow(highResThumbnail,'Parent',axesHandle);   
else
    imHandle = get(axesHandle,'Children');
    oldSize = size(get(imHandle,'CData'));
    if ~isequal(oldSize, size(highResThumbnail))
        imshow(highResThumbnail,'Parent',axesHandle);
    else
        set( imHandle,'CData', highResThumbnail);
    end     
end
end

This is my picture and i want to crop the lymphocyte cell on this picture using that code

After running my code, the result is

How can I save the image on subplot(2,1,2)?

Please do not post screenshots of code. Images cannot be searched, cannot be copied for testing, and impede accessibility. Instead, include relevant code as [formatted text](http://stackoverflow.com/help/formatting). — Meyer, Dec 19 '16 at 15:10
Huh? You mean how to save `highResThumbnail`? `save myfile.mat highResThumbnail`? — Ander Biguri, Dec 19 '16 at 15:47
as you can see, highResThumbnail shown in subplot (2,1,2). I want a picture on a subplot (2,1,2) can be save into 'file.jpg' but I do not know how, if anyone knows how to do it, I would be very grateful — Zilvanhisna Fitri, Dec 19 '16 at 16:18

Cecilia · Accepted Answer · 2016-12-19T23:24:08.937

Edit: I initially read your question too quickly, it looks like you already know how to extract the sub-matrix from your image using the coordinates from imrect because you successfully extract and display highResThumbnail. The only piece you are missing is how to save a matrix as an image.

Use imwrite to save highResThumbnail to any supported image format

For example

imwrite(highResThumbnail, 'thumb.png');

How to use imrect to get a piece of an image

The imrect command only gives you x and y coordinates and width and height. To save that the selected rectangle. Use the coordinates to index into your image matrix. Then, you can save the sub matrix with imwrite.

A = imread('peppers.png');
figure, imshow(A);
h = imrect;
position = wait(h); %Pause until user double clicks on rectangle

%position contains [x y width height]
startx = position(1);
endx = position(1)+position(3);
starty = position(2);
endy = position(2)+position(4);

%Use the coordinates to grab a submatrix of A
B = A(starty:endy, startx:endx, :);
imwrite(B, 'pepper_rect.png');

For subplots, you can only select a rectangle on the active subplot. You can switch between subplots by calling the subplot command again.

%Plot all my images
figure;
subplot(2,1,1);
imshow('peppers.png');

subplot(2,1,2);
imshow('saturn.png');

%Active image is the most recently plotted
h = imrect;
position = wait(h); %Pause until user double clicks on rectangle

%Call subplot again to activate first image
subplot(2,1,1);
h = imrect;
position = wait(h); %Pause until user double clicks on rectangle

I tried using the code that you suggest. I added B = imcrop A (starty: endy, startx: endx, :); but I could not crop the picture, did I miss something or there is something wrong, please correct back @Cecilia. thank you — Zilvanhisna Fitri, Dec 20 '16 at 14:07
I didn't recommend using [`imcrop`](https://www.mathworks.com/help/images/ref/imcrop.html) and you didn't use it in the original code you posted. Are you trying something new? Using `imcrop` would be an alternative to `imrect` for creating the `highresthumbnail` matrix in your example code or the B matrix in my example code, but since you already have that working I'm not sure why you think you need it. — Cecilia, Dec 21 '16 at 15:45

Matlab: how to save the image result Real-time plotting of ROI selected with IMRECT

1 Answers1