uipanel get and redraw image

I am wanting to change the scaling of an image already displayed in a uipanel.

This is my attempt

MM=get(handles.uipanelM,'Children');
J = imadjust(MM,stretchlim(MM),[0 1]);
%imshow(J);
imshow(J,'Parent',handles.uipanelM)
colormap(jet);

I can't figure out how to do it. thanks Jason

Answer 1

[Geoff Hayes]

Jason - If we follow through with what you started (in above) then

 MM=get(handles.uipanelM,'Children');

is the right idea but is making certain assumptions that may be invalid. Does your uipanelM only contain an axes for the image, or does it have other widgets as well? By calling get(handles.uipanelM,'Children');, we will be returned an array of handles to all graphics objects within the uipanelM widget. This may be one, two or more objects, so we can't assume that MM is only one handle, and it definitely won't be our image.

Since the image is already displayed, it must be displayed within an axes object, named (for example) axesM, which will be a child of the uipanelM widget. Rather than doing the above line of code which we would have to modify checking for two or more children, we can get the handle to the graphics object (of type image) that stores the image within the axes as

 hImg = findobj('Parent',handles.axesM,'Type','image');

To get the image data, i.e. the mxnx3 (or whatever dimension) matrix, we can now do

 if ~isempty(hImg)
     % get the image data from the graphics object handle
     imgData = get(hImg,'CData'); 

     % adjust the image
     J = imadjust(imgData,stretchlim(imgData),[0 1]);

     % re-display the image back in the axesM
     imshow(J,'Parent',handles.axesM);

     colormap(jet);
 end

In the above, we retrieve the image data from the axesM widget, adjust the image, and then re-display it back in the axesM widget (and so avoid the uipanelM altogether).

[Jason]

Hi Geoff, thanks for taking time to answer with your good explanaition.

Im not sure how to modify your line below

hImg = findobj('Parent',handles.axesM,'Type','image');

I draw a set of subplots (in a for loop) using the following

hp = handles.uipanelM;
h=subplot('Position',positionVector,'Parent',hp); %to enable deleting use handles

Jason

[Geoff Hayes]

Hi Jason - you will want to either store the handles returned from the subplot calls into an array within the handles object, or you can try the following (which is more like what you started with)

 % get the handles to the axes/subplots within the uipanelM
 hAxes = findobj('Parent',handles.uipanelM,'Type','axes');

 % decide which axes you want to do the adjustment on - if doing both
 % then use a loop
 for k=1:length(hAxes)
     hImg = findobj('Parent',hAxes(k),'Type','image');
     if ~isempty(hImg)
          imgData = get(hImg,'CData'); 
          J = imadjust(imgData,stretchlim(imgData),[0 1]);
          imshow(J,'Parent',hAxes(k));
     end
 end

[Jason]

Perfect, thankyou. the trick was realising that each subplot has its own axes and that each one of these is represented by a handle, hence there are many handles.

So the hieracy is uipanel->axes->image->CData