Функция построения графика

Функция построения графика

private
  FPoints: array [0..144] of TPoint;
 {...}
 procedure TForm1.CalculateGraph;
 var
  xRangePixels, yRangePixels: Integer;
  origin: TPoint;
  radian, interval: Double;
  i: Integer;
 begin
  {
  We calculate the sinus curve in the interval -2Pi..+2Pi,
  with a resolution of 4Pi/144, as a series of points that
  will be connected by a polyline. The graph is scaled to fit into
  the paintbox. The origin of the coordinate system is the center
  of the paintbox. The default windows coordinate system is inverted,
  the Y axis points downward!
 }

  xRangePixels := (paintbox1.Width - 2) div 4; { pixels in Pi }
  yRangePixels := (paintbox1.Height - 2) div 2; { pixels in 1 }
  origin := Point(paintbox1.Width div 2, paintbox1.Height div 2);
  radian := -2.0 * Pi;
  interval := 4.0 * Pi / 144.0;
  for i := 0 to High(FPoints) do
  begin
  FPoints[i].X := origin.x + Round(radian * xRangePixels / Pi);
  FPoints[i].Y := origin.y - Round(sin(radian) * yRangePixels);
  radian := radian + interval;
  end;
 end;
 procedure TForm1.PaintBox1Paint(Sender: TObject);
 var
  origin: TPoint;
  xRangePixels, yRangePixels: Integer;
 begin
  with PaintBox1.Canvas do
  begin
  { Fill background in white }
  Brush.Color := clBtnFace;
  Brush.Style := bsSolid;
  Fillrect(paintbox1.BoundsRect);
  { Paint a coordinate cross }
  origin := Point(paintbox1.Width div 2, paintbox1.Height div 2);
  Pen.Color := clBlack;
  Pen.Style := psSolid;
  Pen.Width := 1;
  MoveTo(1, origin.Y);
  LineTo(paintbox1.Width - 1, origin.y);
  MoveTo(origin.x, 1);
  LineTo(origin.x, paintbox1.Height - 1);
  { Paint some tickmarks and label the axis }
  Font.Name  := 'Symbol';
  Font.Size := 8;
  Font.Color := clBlack;
  xRangePixels := (paintbox1.Width - 2) div 4; { pixels in Pi }
  yRangePixels := (paintbox1.Height - 2) div 2; { pixels in 1 }
  { X axis }
  MoveTo(origin.x - 2 * xRangePixels, origin.y - 4);
  LineTo(origin.x - 2 * xRangePixels, origin.y + 4);
  TextOut(origin.x - 2 * xRangePixels + 2, origin.y + 2, '-2p');
  MoveTo(origin.x - xRangePixels, origin.y - 4);
  LineTo(origin.x - xRangePixels, origin.y + 4);
  TextOut(origin.x - xRangePixels + 2, origin.y + 2, '-p');
  MoveTo(origin.x + xRangePixels, origin.y - 4);
  LineTo(origin.x + xRangePixels, origin.y + 4);
  TextOut(origin.x + xRangePixels - 2 - TextWidth('p'), origin.y + 2, 'p');
  MoveTo(origin.x + 2 * xRangePixels, origin.y - 4);
  LineTo(origin.x + 2 * xRangePixels, origin.y + 4);
  TextOut(origin.x + 2 * xRangePixels - 2 - TextWidth('2p'), origin.y + 2, '2p');

  { Y axis }
  MoveTo(origin.x - 4, origin.y - yRangePixels);
  LineTo(origin.x + 4, origin.y - yRangePixels);
  TextOut(origin.x + 4, origin.y - yRangePixels, '1.0');
  MoveTo(origin.x - 4, origin.y - yRangePixels div 2);
  LineTo(origin.x + 4, origin.y - yRangePixels div 2);
  TextOut(origin.x + 4, origin.y - (yRangePixels + TextHeight('1')) div 2, '0.5');
  MoveTo(origin.x - 2, origin.y + yRangePixels div 2);
  LineTo(origin.x + 2, origin.y + yRangePixels div 2);
  TextOut(origin.x + 3, origin.y + (yRangePixels - TextHeight('1')) div 2, '-0.5');
  MoveTo(origin.x - 2, origin.y + yRangePixels);
  LineTo(origin.x + 2, origin.y + yRangePixels);
  TextOut(origin.x + 3, origin.y + yRangePixels - TextHeight('1'), '-1.0');
  {Paint the graph }
  Pen.Color := clBlue;
  Polyline(FPoints);
  end;
 end;
 procedure TForm1.FormResize(Sender: TObject);
 begin
  CalculateGraph;
 end;
 procedure TForm1.FormCreate(Sender: TObject);
 begin
  CalculateGraph;
 end;
Взято с сайта: http://www.swissdelphicenter.ch

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