ptil

function PointInLineEx(p, p1, p2: TPoint; tol: Integer): Boolean;
var
  x, y, l, d: Integer;
  t, s, c: Extended;
begin
  if (tol > 0) then
    d := (Abs(tol) + 1)
  else
    d := 1;
  t := ArcTan2((p2.Y - p1.Y), (p2.X - p1.X));
  s := Sin(t);
  c := Cos(t);
  x := Round((c * (p.X - p1.X)) + (s * (p.Y - p1.Y)));
  y := Round((c * (p.Y - p1.Y)) - (s * (p.X - p1.X)));
  l := Round((c * (p2.X - p1.X)) + (s * (p2.Y - p1.Y)));
  Result:= (((y > -d) and (y < d)) and ((x > -d) and (x < (l + d))));
end;

function PointInLine(p, p1, p2: TPoint): Boolean;
begin
  Result := PointInLineEx(p, p1, p2, 0);
end;

var
  a, b, c: TPoint;

procedure DebugBitmap(bmp: Integer);
var
  w, h: Integer;
begin
  GetBitmapSize(bmp, w, h);
  DisplayDebugImgWindow(w, h);
  DrawBitmapDebugImg(bmp);
end;

var
  x, y: Integer;
  bmp: Integer;

begin
  a := Point(175, 269);
  b := Point(259, 344);
  c := Point(216, 298);
  bmp := CreateBitmap(500, 500);
  for x := 0 to 499 do
    for y := 0 to 499 do
      if PointInLineEx(Point(x, y), a, b, 15) then
        FastSetPixel(bmp, x, y, 255);
  for x := 0 to 499 do
    for y := 0 to 499 do
      if PointInLine(Point(x, y), a, b) then
        FastSetPixel(bmp, x, y, 16777215);
  DebugBitmap(bmp);
  FreeBitmap(bmp);
end.