How do I link an image and a histogram of that image so the histogram only represents what is shown in the image, i.e. if I zoom in on the image, the histogram updates?

I have a gui with two axes, an image (created using imagesc) and a histogram of that image. I want to add a menu item that will allow the user to turn on/off the ability to link the histogram to the image so if the user zooms in/out, the histogram automatically updates with the image data that is shown (and ignore the image data that is not shown).

I am using Matlab 2016a.

Any suggestion is welcome.

Thanks!

Answer 1

[Jason]

I was able to get this to work by setting the ActionPostCallback for the zoom function to call a custom function.

set(zoom(obj.ax1), 'ActionPostCallback',@(x,y) obj.redrawHistogram(obj.ax1));

and inside the redrawHistogram function I redraw the histogram based on the data being displayed.

Answer 2

[Image Analyst]

Use an imscrollpanel to contain your image and then call "getVisibleImageRect()":

% Here's the example from the documentation:
% Create a scroll panel with a Magnification Box and an Overview tool.
hFig = figure('Toolbar', 'none',...
              'Menubar', 'none');
hIm = imshow('saturn.png');
hSP = imscrollpanel(hFig,hIm); % Handle to scroll panel.
set(hSP,'Units', 'normalized',...
        'Position', [0, .1, 1, .9])
  
% Add a Magnification Box and an Overview tool.
hMagBox = immagbox(hFig, hIm);
boxPosition = get(hMagBox, 'Position');
set(hMagBox,'Position', [0, 0, boxPosition(3), boxPosition(4)])
imoverview(hIm)

% Get the scroll panel API to programmatically control the view.
api = iptgetapi(hSP);
% Get the current magnification and position.
mag = api.getMagnification();
r = api.getVisibleImageRect();

The full demo is attached.