macro 'Image Correlation [I]';
{Generates an XY plot indicating how well correlated two images are.  
It uses the z-value of a given pixel in a certain slice as the x-coordinate; 
z-value of the corresponding pixel in another slice as the y-coordinate.  
These are plotted into a new window to give a scatter plot.  The 
percentage done is shown in the Info window.}

var
   xmin, xmax, ymin, ymax, xscale, yscale, Percent: real;
   xslice, yslice, nPixels, ticks: integer;
   width, height, x, y, xvalue, yvalue, Pointvalue: integer;
   wide, high, StackID, PlotID, margin, ticksize: integer;
   time: real;
begin
   if nSlices=0 then begin
      beep;
      PutMessage('This macro requires a stack.');
      exit
   end;
   SaveState;
   InvertY(true);
   KillRoi;
   GetPicSize(wide, high);
   nPixels:=wide * high;
   Measure;
   StackID := PidNumber;
   xslice := GetNumber('Slice to plot on the x-axis:', 1);
   yslice := GetNumber('Slice to plot on the y-axis:', 2);
   width := 256;
   height := 256;
   SetNewSize(width,height);
   SetForeground(255);
   SetBackground(0);
   MakeNewWindow('Plot');
   InvertY(true);
   PlotID := PicNumber;
   SelectPic(StackID);
   SetCursor('watch');
   ticks := TickCount;

   for y := 0 to high - 1 do begin
      for x := 0 to wide - 1 do begin
         ChoosePic(StackID);
         ChooseSlice(xslice);
         xvalue:=GetPixel(x, y);  {ie z-value of pixel (x,y) on one slice}
         ChooseSlice(yslice);
         yvalue:=GetPixel(x, y); {ie z-value of same pixel on other slice}
         ChoosePic(PlotID);
         Pointvalue := GetPixel(xvalue, 255 - yvalue);
         if PointValue < 254
            then PointValue:=PointValue+1;
         PutPixel(xvalue, 255 - yvalue, PointValue);
     end; {for x...}
     if (y mod 10) = 0
         then ShowMessage((y / high) * 100:2:0, '% done');
   end;  {for y...}

   time := (TickCount-ticks) / 60;
   ShowMessage(nPixels:1,  ' pixels\',  time:1:2,  ' seconds\',
      nPixels/time:1:0,  ' pixels/second');

   SelectPic(StackID);
   SelectSlice(xSlice);
   SelectPic(PlotID);
   SelectAll;
   EnhanceContrast;
   ApplyLut;
   SelectAll;
   Copy;
   Dispose;
   margin := 75;
   ticksize := 6;
   SetNewSize(width + (2 * margin), height + (2 * margin));
   SetForeground(255);
   SetBackground(0);
   MakeNewWindow('Correlation Plot');
   SetFont('Geneva');
   SetFontSize(9);
   InvertY(true);
   MakeRoi(margin, margin, 256, 256);
   Paste;
   MakeRoi(margin - 1, margin - 1, 258, 258);
   SetLinewidth(1); 
   DrawBoundary;
   KillRoi;
   MoveTo(margin, margin + 255);
   LineTo(margin, margin + 255 + ticksize);
   MoveTo(margin + 50, margin + 256);
   LineTo(margin + 50, margin + 256 + ticksize);
   MoveTo(margin + 100, margin + 256);
   LineTo(margin + 100, margin + 256 + ticksize);
   MoveTo(margin +150, margin + 256);
   LineTo(margin + 150, margin + 256 + ticksize);
   MoveTo(margin + 200, margin + 256);
   LineTo(margin + 200, margin + 256 + ticksize);
   MoveTo(margin + 255, margin + 256);
   LineTo(margin + 255, margin + 256 + ticksize);
   MoveTo(margin - 1, margin + 255);
   LineTo(margin - ticksize, margin + 255);
   MoveTo(margin - 1, margin + 206);
   LineTo(margin - ticksize, margin + 206);
   MoveTo(margin -1 , margin + 156);
   LineTo(margin - ticksize, margin + 156);
   MoveTo(margin - 1, margin + 106);
   LineTo(margin - ticksize, margin + 106);
   MoveTo(margin - 1, margin + 56);
   LineTo(margin - ticksize, margin + 56);
   MoveTo(margin - 1, margin);
   LineTo(margin - ticksize, margin);
   MoveTo(margin - 25, margin);
   Writeln('255');
   MoveTo(margin - 25, margin + 56);
   Writeln('200');
   MoveTo(margin - 25, margin + 156);
   Writeln('100');
   MoveTo(margin - 14, margin + 256);
   Writeln('0');
   MoveTo(margin - 2, margin + 270);
   Writeln('0');
   MoveTo(margin + 92, margin + 270);
   Writeln('100');
   MoveTo(margin + 192, margin + 270);
   Writeln('200');
   MoveTo(margin + 248, margin + 270);
   Writeln('255');
   MoveTo(margin + 70, margin + 290);
   Writeln('Z-value on slice', xslice:1);
   MoveTo(margin - 65, margin + 100);
   Writeln('Z-value');
   MoveTo(margin - 65, margin + 115);
   Writeln('on slice', yslice:1);

   RestoreState;
end;