procedure TformMain.ImageEnViewSourceMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
var
  mousePos, clientPos: TPoint;
  rect: TRect;
begin
  // Get the position of the mouse cursor in screen coordinates:
  GetCursorPos(mousePos);

  // Convert the screen coordinates of the mouse cursor to client coordinates
  // relative to the top-left corner of the Source ImageEnView:
  clientPos := ImageEnViewSource.ScreenToClient(mousePos);

  // Define the rectangle to be copied from the Source ImageEnView's control:
  rect.Left := clientPos.X - 50;
  rect.Top  := clientPos.Y - 50;
  rect.Right := rect.Left + 100;
  rect.Bottom := rect.Top + 100;

  // Copy the 100 x 100 area from the Source ImageEnView's control to the Target ImageEnView:
  ImageEnViewSource.IEBitmap.CopyRectTo(
    ImageEnViewPreviewMouseCursor.IEBitmap, // source control
    rect.Left, // source rectangle left
    rect.Top,  // source rectangle top
    0, // destination rectangle left
    0, // destination rectangle top
    rect.Width, // rectangle width
    rect.Height // rectangle height
    );
  //ImageEnViewPreviewMouseCursor.Zoom := 200; // TImageEnView.Zoom is not published!
  CodeSite.Send('TformMain.ImageEnViewSourceMouseMove: ');
end;

// Convert the screen coordinates of the mouse cursor to client coordinates
// relative to the top-left corner of the Source ImageEnView:
clientPos := ImageEnViewSource.ScreenToClient(mousePos);

bitmapX := hyieutils.imin(hyieutils.imax(0, ImageEnViewSource.XScr2Bmp(X)), ImageEnViewSource.IEBitmap.Width - 1);
bitmapY := hyieutils.imin(hyieutils.imax(0, ImageEnViewSource.YScr2Bmp(Y)), ImageEnViewSource.IEBitmap.Height - 1);

// Define the rectangle to be copied from the ImageEnView's control:
rect.Left := bitmapX - 50;
rect.Top  := bitmapY - 50;
rect.Right := rect.Left + 100;
rect.Bottom := rect.Top + 100;