Zooming Out and Zooming In (C++ Builder 3.0)

Take the following steps to add code that can reduce and enlarge the displayed size of the image. This demonstrates the scaling properties that are normally used for zooming in and zooming out. It emphasizes the relationship of the displayed rectangle to the LEAD control.

1. Start with the project that you created in Loading and Displaying an Image.

2. Add two command buttons to your form and name them as follows:

3. Code the ZoomIn button's click procedure as follows:

void __fastcall TForm1::ZoomInClick(TObject *Sender)
{
  LEAD1->AutoSetRects = True;
  LEAD1->PaintSizeMode = PAINTSIZEMODE_ZOOM;
  LEAD1->PaintZoomFactor = LEAD1->PaintZoomFactor + 10;
}

4. Code the ZoomOut button's click procedure as follows:

void __fastcall TForm1::ZoomOutClick(TObject *Sender)
{
  LEAD1->AutoSetRects = True;
  LEAD1->PaintSizeMode = PAINTSIZEMODE_ZOOM;
  if (LEAD1->PaintZoomFactor > 10)
      LEAD1->PaintZoomFactor = LEAD1->PaintZoomFactor - 10;
}

5. Run your program to test it.