pixval.m

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function pixval(arg1, arg2)
%PIXVAL Display information about image pixels.
%   PIXVAL ON turns on interactive display of information about image pixels
%   in the current figure. PIXVAL installs a black bar at the bottom of the
%   figure which displays the row-column coordinates for whatever pixel the
%   cursor is currently over, and the color information for that pixel. If
%   the image is binary or intensity, the color information is a single
%   intensity value. If the image is indexed or RGB, the color information
%   is an RGB triplet. The values displayed are the actual data values,
%   regardless of the class of the image array, or whether the data is in
%   normal image range.
%
%   If you click on the image and hold down the mouse button while you move
%   the cursor, PIXVAL also displays the Euclidean distance between the
%   point you clicked on and current cursor location. PIXVAL draws a line
%   between these points to indicate the distance being measured. When you
%   release the mouse button, the line and the distance display disappear.
%
%   You can move the display bar by clicking on it and dragging it to
%   another place in the figure.
%
%   PIXVAL OFF turns interactive display off in the current figure. You can
%   also turn off the display by clicking the button on the right side of
%   the display bar.
%
%   PIXVAL toggles interactive display on or off in the current figure.
%
%   PIXVAL(FIG,OPTION) applies the PIXVAL command to the figure specified
%   by FIG. OPTION is string containing 'on' or 'off'.
%
%   Remarks
%   -------
%   PIXVAL conflicts with certain other functions, such as ZOOM
%   and ROTATE3D, that enable you to use a mouse to interact
%   with the figure.  Use only one of these functions at a time.
%
%   See also IMPIXEL, IMPROFILE.

%   Chris Griffin 6-9-97
%   Copyright 1993-1998 The MathWorks, Inc.  All Rights Reserved.
%   $Revision: 1.7 $  $Date: 1997/11/24 15:36:06 $

error(nargchk(0,2,nargin));

if nargin==0
   arg1 = gcf;
end

if ischar(arg1) % execute a callback
   switch lower(arg1)
   case 'pixvalmotionfcn'
      PixvalMotionFcn;
   case 'buttondownonimage'
      ButtonDownOnImage;
   case 'backtonormalpixvaldisplay'
      BackToNormalPixvalDisplay;
   case 'movedisplaybar'
      MoveDisplayBar;
   case 'on'
      pixval(gcf, 'on');
   case 'off'
      pixval(gcf, 'off');
   case 'deletedisplaybar'
      DeleteDisplayBar;
   otherwise
      error(['Unknown PIXVAL command or callback: ' arg1 '.']);
   end 
   
elseif ishandle(arg1)
   images = findobj(arg1, 'type', 'image');
   if isempty(images)
      return
   end
   
   figureHandle = get(get(images(1), 'parent'), 'parent');
     
   if nargin>1   % pixval(handle, 'on|off')
      if ischar(arg2)
         if strcmp(lower(arg2), 'off')
            action = 'destroy';
         elseif strcmp(lower(arg2), 'on')
            action = 'create';
         else
            error(['Unknown PIXVAL input string: ' arg2]);
         end
      else
         error('Invalid input arguments');
      end
   else  % pixval(handle) or pixval
      % Toggle the state
      displayBar = findobj(figureHandle, 'tag', 'pixel value display bar');
      if isempty(displayBar)
         action = 'create';
      else
         action = 'destroy';
      end 
   end
      
   % Put things in the Images' UserData so that pixel value display works
   switch action
   case 'destroy'
      displayBar = findobj(figureHandle, 'tag', 'pixel value display bar');
      if ~isempty(displayBar)
         DeleteDisplayBar(displayBar);
      end  
      
   case 'create'
      otherDisplayBar = findobj(figureHandle, 'tag', 'pixel value display bar');
      if ~isempty(otherDisplayBar)
         % Pixval is already ON for this figure.
         return
      end
      
      % Save the interactive state of the figure. We decided to never 
      % restore the old figure info, but I'll hang onto it anyways!
      dbud.oldFigureUIState = uisuspend(figureHandle);
      
      % Make sure that the Motion function doesn't interrupt itself
      set(figureHandle, 'Interruptible', 'off', 'busyaction', 'queue');
      
      % Make sure that the Image's Button Down & Up functions will queue
      set(images, 'Interruptible', 'off', 'BusyAction', 'Queue');
         
      % dbud is the UserData structure which is going into the display bar
      dbud.figureHandle = figureHandle;
      dbud.displayMode = 'normal'; 
      
      figPos = get(dbud.figureHandle, 'position');
      tempStr = sprintf(' %3d, %3d = %6.4f,%6.4f,%6.4f  dist = %3.3f', ...
         9999,9999,pi/10,pi/10,pi/10,pi*100);
            
      % Calculate the position vector of the display bar      
      tempTxt = uicontrol('Parent', dbud.figureHandle, 'horiz', 'left', ...
         'Style', 'text', 'Units', 'pixels', 'visible', 'off', 'fontname', ...
         'Courier','String', tempStr, 'position', [0 0 figPos(3) 20]);
      extent= get(tempTxt, 'extent');
      txtHt = extent(4); 
      txtWid = extent(3)+txtHt; % Leave room for the close button
      delete(tempTxt);
      
      % Create position vectors for Text, Frame, and Close Button
      pos = [0 0 min(txtWid,figPos(3))-txtHt txtHt];
      btnSide = pos(4)-4;  % In pixels
      btnPos = [pos(1)+pos(3)+2 pos(2)+2 btnSide btnSide];
      frmPos = [pos(1)+pos(3) 0 txtHt txtHt];
      
      % Create a frame for the display bar. I do this because of a bug in 
      % MATLAB 5.2 where the text field pops to the front of the button each
      % time it is updated.  It should stay behind in which case, all we would
      % need is the text uicontrol and the button.  We can take the frame out
      % if the bug gets fixed.  Make sure the frame doesn't fall behind the 
      % text control, otherwise you can't execute the text control's buttondown
      % function (another MATLAB 5.2 bug).

      dbud.DisplayFrame = uicontrol('Parent', figureHandle, ...
         'style', 'frame', ...
         'Units', 'pixels', ...
         'Position', frmPos, ...
         'Background', [0 0 0], ...
         'BusyAction', 'queue', ...
         'Interruptible', 'off');
         
      % Create the display bar
      dbud.buttonDownImage = 0;  % Image 0 never exists      
      DisplayBar = uicontrol('Parent', figureHandle, ...
         'Style','text', ...
         'Units','pixels', ...
         'Position',pos, ...
         'Foreground', [1 1 .5], ...
         'Background', [0 0 0], ...
         'Horiz','left', ...
         'Tag', 'pixel value display bar', ...
         'String','', ...
         'fontname', 'Courier', ...
         'BusyAction', 'queue', ...
         'enable', 'inactive', ...
         'ButtonDownFcn', 'pixval(''MoveDisplayBar'')', ...
         'DeleteFcn', 'pixval(''DeleteDisplayBar'')', ...
         'Interruptible', 'off');
            
      % Create the close button
      dbud.CloseButton = uicontrol('Parent', figureHandle, ...
         'style', 'pushbutton', ...
         'units', 'pixels', ...
         'position', btnPos, ...
         'String', 'X', ...
         'Callback', 'pixval(''DeleteDisplayBar'')', ...
         'BusyAction', 'queue', ...
         'DeleteFcn', 'pixval(''DeleteDisplayBar'')', ...
         'Interruptible', 'off');
      
      % Register the motion function and button up function
      set(figureHandle, 'WindowButtonMotionFcn',...
         'pixval(''PixvalMotionFcn'')')
      
      set(DisplayBar, 'UserData', dbud);
      PixvalMotionFcn(DisplayBar);
   end
   
else 
   error('Invalid input argument.')
end 



%%%
%%%  Sub-function - PixvalMotionFcn
%%%

function PixvalMotionFcn(displayBar)

if nargin<1
   displayBar = findobj(gcbf, 'Tag', 'pixel value display bar');
end

if isempty(displayBar)
   % Pixval is in a half-broken state.  Another function (like zoom) has
   % restored pixval callbacks and PIXVAL has already been uninstalled.
   % Call uisuspend to gracefully get rid of the callbacks.
   uisuspend(gcbf);
   return
end

dbud = get(displayBar, 'UserData');
pt = get(dbud.figureHandle, 'CurrentPoint');
x = pt(1,1); y = pt(1,2);

if strcmp(dbud.displayMode, 'normal') 
   % See if we're above the displayBar
   dbpos = get(displayBar, 'Position');
   left   = dbpos(1);
   bottom = dbpos(2);
   width  = dbpos(3);
   height = dbpos(4);
   if x>=left & x<=left+width & y>=bottom & y<=bottom+height
      % We're hovering above the display bar
      
      % Look to see if we are above the Close button
      cp = get(dbud.CloseButton, 'Position');
      if  x>=cp(1) & x<=cp(1)+cp(3) & y>=cp(2) & y<=cp(2)+cp(4)
         if isfield(dbud, 'oldPointer') % Switch back to the default pointer
            set(dbud.figureHandle, 'Pointer', dbud.oldPointer, ...
               'PointerShapeCData', dbud.oldPointerShapeCData, ...
               'PointerShapeHotSpot', dbud.oldPointerShapeHotSpot);
            dbud = rmfield(dbud, {'oldPointer', ... 
                  'oldPointerShapeCData', 'oldPointerShapeHotSpot'});
         end
      else
         % Save the default pointer if there is one
         if ~isfield(dbud, 'oldPointer') % We still have the default pointer
            dbud.oldPointer = get(dbud.figureHandle, 'Pointer');
            dbud.oldPointerShapeCData = get(dbud.figureHandle, 'PointerShapeCData');
            dbud.oldPointerShapeHotSpot = get(dbud.figureHandle, 'PointerShapeHotSpot');
         end
         setptr(dbud.figureHandle, 'hand'); 
      end
   else 
      % We're not hovering over the display bar 
      [imageHandle,imageType,img,x,y] = OverImage(dbud.figureHandle);
      if imageHandle ~= 0       
         % Save old pointer and get a new one (use Custom pointer for non-Windows machine)
         if ~isfield(dbud, 'oldPointer') % We still have the default pointer
            dbud.oldPointer = get(dbud.figureHandle, 'Pointer');
            dbud.oldPointerShapeCData = get(dbud.figureHandle, 'PointerShapeCData');
            dbud.oldPointerShapeHotSpot = get(dbud.figureHandle, 'PointerShapeHotSpot');
         end
         if strcmp(computer, 'PCWIN')
            set(dbud.figureHandle, 'Pointer', 'cross');
         else
            [pointerShape, pointerHotSpot] = CreatePointer;
            set(dbud.figureHandle, 'Pointer', 'custom', ...
               'PointerShapeCData', pointerShape, ...
               'PointerShapeHotSpot', pointerHotSpot);
         end
         
         % Update the Pixel Value display
         UpdatePixelValues(imageHandle, imageType, displayBar,img,x,y);
      else
         if isfield(dbud, 'oldPointer') % Switch back to the default pointer
            set(dbud.figureHandle, 'Pointer', dbud.oldPointer, ...
               'PointerShapeCData', dbud.oldPointerShapeCData, ...
               'PointerShapeHotSpot', dbud.oldPointerShapeHotSpot);
            dbud = rmfield(dbud, {'oldPointer', ... 
                  'oldPointerShapeCData', 'oldPointerShapeHotSpot'});
            set(displayBar, 'String', '');
         end
      end
   end
elseif strcmp(dbud.displayMode, 'distance') 
   % If we're in distance mode and in another image, clean up a bit.
   [imageHandle,imageType,img,x,y]= OverImage(dbud.figureHandle);
   if imageHandle~=0 
      if imageHandle==dbud.buttonDownImage
         UpdatePixelValues(imageHandle, imageType, displayBar,img,x,y);