SmoothPath

procedure SmoothPath(const points: TPathD; isClosedPath: Boolean; tension: double = 0; shapeTolerance: double = 0.1): TPathD;


This function performs bicubic interpolation to convert discrete points in a path into a close approximation of a smooth curve. Paths may be open or closed.

tension: Range between -1 and 1 where -1 will produce the most curving, and +1 will produce the least (ie virtually no) curving.

shapeTolerance: the minimum distance a vertex can be from an imaginary line drawn between its two adjacent vertices (see SimplifyPaths).

uses Img32, Img32.Fmt.PNG, Img32.Draw, Img32.Extra;
...
var
  i: integer;
  img: TImage32;
  path, smoothedPath: TPathD;
  rec: TRect;
begin
  path :=  MakePath([190,120, 240,160, 560,120, 190,490]);
  // smooth closed path with normal smoothing 
  smoothedPath := SmoothPath(path, true, 0);
  // smooth closed path with maximum smoothing 
  //smoothedPath := SmoothPath(path, true, -1);
  rec := GetBounds(smoothedPath);
  Types.InflateRect(rec, margin, margin);
  path := TranslatePath(path, -rec.Left, -rec.Top);
  smoothedPath := 
    TranslatePath(smoothedPath, -rec.Left, -rec.Top);
  
  img := TImage32.Create(rec.Width, rec.Height);
  DrawLine(img, path, 1, clRed32, esClosed);
  DrawLine(img, smoothedPath, 3, clBlue32, esClosed);
  for i := 0 to High(path) do
    DrawPoint(img, path[i], 3, clRed32);
  img.SaveToFile('interpolation.png');
  img.Free;
with normal smoothing (0) with maximum smoothing (-1) 
uses Img32, Img32.Fmt.PNG, Img32.Draw, Img32.Extra;
...
var
  i: integer;
  img: TImage32;
  path, smoothedPath: TPathD;
  rec: TRect;
begin
  path := MakePath([10,100, 60,50, 110,50, 160,10, 210,100]);
  // smooth open path with normal smoothing 
  smoothedPath := SmoothPath(path, false, 0);
  rec := GetBounds(smoothedPath);
  Types.InflateRect(rec, margin, margin);
  path := TranslatePath(path, -rec.Left, -rec.Top);
  smoothedPath := TranslatePath(smoothedPath, -rec.Left, -rec.Top);

  img := TImage32.Create(rec.Width, rec.Height);
  DrawLine( img, smoothedPath, 3, clBlue32, esRound, jsRound);
  for i := 0 to High(path) do
    DrawPoint(img, path[i], 3, clRed32);
  img.SaveToFile('interpolation2.png');
  img.Free;

See Also

SimplifyPaths