MATLAB可视化：用鼠标选取ROI

function Zoomer
    figure();

    highResImage = imread('peppers.png');
    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

回调函数中，主要实现以下功能：

1. 判断axes2是否为空，如果为空，imshow();
2. 不为空，说明已经有图在显示了。
3. 看一下现在的尺寸和现在框选区域的大小。如果相同，直接把里面的cdata设置成新的。
4. 如果尺寸不同，那就重新imshow();

 imHandle = get(axesHandle,'Children');

oldSize = size(get(imHandle,'CData'));

其中Cdata指的是”所画图像中使用到的数据“。这里就是的到的图像矩阵。

解决方案2：

function imZ = Zoom(im, s)

f = figure;
a1 = subplot(1,2,1);
imshow(im,'InitialMagnification', 'fit');
a2 = subplot(1,2,2);
imshow(im,'InitialMagnification', 'fit');

Ipos = [0 0 s];
rect = imrect(a1,Ipos);
rect.setPositionConstraintFcn(@(p) Const(p,size(im)));
rect.addNewPositionCallback(@(p) CB(p,a2));
CB(Ipos,a2);

if nargout > 0
    uiwait(f);
    imZ = im(pm(2):pm(2)+pm(4),pm(1):pm(1)+pm(3),:);
end

    function p = Const(p,imS)
        p(1:2) = max(1,p(1:2));
        p(1:2) = min(imS([2 1])-p(3:4),p(1:2));
    end

    function CB(p,a)
        pm = round(p);
        axes(a);       
        axis([pm(1),pm(1)+pm(3),pm(2),pm(2)+pm(4)]);
    end
end

参考来源：

Matlab: Real-time plotting of ROI selected with IMRECT

matalb parent and children

Using parent child relationships to find figures