Macro 'Help on Ferets Diameter [F1]';
var
  s1:string;
begin
  s1:='Select object of interest using the wand tool.';
  s1:=concat(s1,'  After selecting object, execute the Ferets Diameter Macro');
  s1:=concat(s1,' from the Special Menu or by pressing:\\[F2]:  Using distance between xyCoordinate arrays');
  s1:=concat(s1,'\\[F3]:  Using height/width of rotated object');
  ShowMessage(s1);
  SelectWindow('Info');
  SelectTool('wand');
end;

{This macro calculates the object of interest's Feret's Diameter by}
{calculating the distance between successive points (user defines  }
{increment between successive points, 1 being the slowest but most }
{accurate) from the ROI Coordinate arrays within NIH Image.        }

Macro 'Ferets Diameter:  Coordinate Arrays [F2]';
var
   i,j,k,increment:integer;
begin
  increment:=GetNumber('Increment between array points:',1,0);
  i:=1;
  While i<=nCoordinates do
    begin
      j:=i+increment;
      While j<=nCoordinates do
        begin
          if SQRT(SQR(xCoordinates[i]-xCoordinates[j])+SQR(yCoordinates[i]-yCoordinates[j]))>k
            then k:=SQRT(SQR(xCoordinates[i]-xCoordinates[j])+SQR(yCoordinates[i]-yCoordinates[j]));
          j:=j+increment;
        end;
      i:=i+increment;
    end;
  PutMessage(concat('The Ferets Diameter is ',k:0,' pixels'));
end;

{This macro calculates the object of interest's Feret's Diameter by}
{calculating the height and width of the objects rectangular ROI at}
{a series of angles between 0 and 90 degrees of object rotation.   }
{It works for a binary object on a white background only (although }
{it could easily be modified to work with a thresholded greyscale  }
{image).  Errors in object selection after rotation can occur if   }
{the object is segmented by the process of rotation (try dilating  }
{the object before running the macro and subtracting 2 from the    }
{final result.  Also, as a rule of thumb the image window should   }
{be twice the size of the object to allow for rotation.            }

Macro 'Ferets Diameter:  Rotated Object [F3]';
var
  i,left,top,width,height,feret,increment:integer;
begin
  SetScaling('Nearest,Same Window');
  GetRoi(left,top,width,height);
  if width>height then feret:=width else feret:=height;
  increment:=GetNumber('Enter rotation increment:',15,0);
  for i:=1 to (trunc(90/increment)-1) do
    begin
      SelectAll;
      ScaleandRotate(1,1,increment);
      AutoOutline(0,trunc(top+height/2));
      GetRoi(left,top,width,height);
      if width>Feret then feret:=width;
      if height>Feret then feret:=height;
    end;
  PutMessage(concat('The Ferets Diameter is ',feret:0,' pixels'));
end;