绘画32：带鼠标拖盘的锅，用鼠标轮缩放到鼠标光标

Question

，并看到了其内置的滚动条，

.Scale

允许其中一些。至少要走得那么远是非常容易的。

Graphics32是这种事情的好工具吗？还有我可能会研究的其他（也许更简单）的工具吗？

任何人都有任何有关如何实施上述的指针或示例代码？

• Graphics32提供了一个名为Timgview32的组件，该组件可以通过设置比例属性来缩小。这样做的适当方法是使用onMouseWheelup和-down事件。将TabStop设置为true以触发这些事件并将其设置为false。但是以这种方式缩放不符合您将鼠标光标放大操作集中的愿望。因此，重新定位和调整大小是一个更好的解决方案。此外，据我了解，图像始终在组件的左上角对齐，因此也必须通过重新定位组件来完成平移。

  uses
    Windows, Classes, Controls, Forms, GR32_Image, GR32_Layers, Jpeg;
  
  type
    TForm1 = class(TForm)
      ImgView: TImgView32;
      procedure FormCreate(Sender: TObject);
      procedure ImgViewMouseWheel(Sender: TObject; Shift: TShiftState;
        WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
      procedure ImgViewMouseDown(Sender: TObject; Button: TMouseButton;
        Shift: TShiftState; X, Y: Integer; Layer: TCustomLayer);
      procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
        Y: Integer);
      procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
        Shift: TShiftState; X, Y: Integer);
    private
      FDragging: Boolean;
      FFrom: TPoint;
    end;
  
  implementation
  
  {$R *.dfm}
  
  procedure TForm1.FormCreate(Sender: TObject);
  begin
    ImgView.Bitmap.LoadFromFile('D:\Pictures\Mona_Lisa.jpg');
    ImgView.TabStop := True;
    ImgView.ScrollBars.Visibility := svHidden;
    ImgView.ScaleMode := smResize;
  end;
  
  procedure TForm1.ImgViewMouseWheel(Sender: TObject; Shift: TShiftState;
    WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
  const
    ZoomFactor: array[Boolean] of Single = (0.9, 1.1);
  var
    R: TRect;
  begin
    MousePos := ImgView.ScreenToClient(MousePos);
    with ImgView, MousePos do
      if PtInRect(ClientRect, MousePos) then
      begin
        R := BoundsRect;
        R.Left := Left + X - Round(ZoomFactor[WheelDelta > 0] * X);
        R.Top := Top + Y - Round(ZoomFactor[WheelDelta > 0] * Y);
        R.Right := R.Left + Round(ZoomFactor[WheelDelta > 0] * Width);
        R.Bottom := R.Top + Round(ZoomFactor[WheelDelta > 0] * Height);
        BoundsRect := R;
        Handled := True;
      end;
  end;
  
  procedure TForm1.ImgViewMouseDown(Sender: TObject; Button: TMouseButton;
    Shift: TShiftState; X, Y: Integer; Layer: TCustomLayer);
  begin
    FDragging := True;
    ImgView.Enabled := False; { Temporarily, to get MouseMove to the parent }
    FFrom := Point(X, Y);
  end;
  
  procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
    Y: Integer);
  begin
    if FDragging then
      ImgView.SetBounds(X - FFrom.X, Y - FFrom.Y, ImgView.Width, ImgView.Height);
  end;
  
  procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
    Shift: TShiftState; X, Y: Integer);
  begin
    FDragging := False;
    ImgView.Enabled := True;
    ImgView.SetFocus;
  end;

• eDIT：
替代司法，而不是timgview32：

Answer 1