使用剪切板[2]: Assign、HasFormat

准备工作:
在窗体上放置一个 TPanel; 在 TPanel 上放一个 TImage; 另外需要三个按钮.

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本例效果图:

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第一版代码:

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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Panel1: TPanel;
    Image1: TImage;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses Clipbrd;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Image1.Left := 0;
  Image1.Top := 0;
  Panel1.AutoSize := True;
  Image1.AutoSize := True;
  Image1.Picture.LoadFromFile('c:\temp\test.bmp');

  TButton(Sender).Caption := '导入';
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Clipboard.Assign(Image1.Picture); {把 Image1 中的图片放入剪切板}
  {现在在图像软件中都可以粘贴了, 可以用 Windows 画图板试试}

  TButton(Sender).Caption := '复制';
end;

procedure TForm1.Button3Click(Sender: TObject);
var
  bit: TBitmap; {准备用一个 TBitmap 从剪切板中结束图片}
  x,y: Integer;
begin
  bit := TBitmap.Create;
  bit.Assign(Clipboard);               {从剪切板获取}
  x := Panel1.Width + Panel1.Left * 2; {x,y 是准备在窗体上的粘贴位置}
  y := Panel1.Top;
  Canvas.Draw(x, y, bit);              {粘贴就是画出来呗}
  bit.Free;

  TButton(Sender).Caption := '粘贴';
end;

end.

不过现在程序还有漏洞: 假如剪切板中没有东西, 粘贴什么? 如果剪切板中不是图片, 怎么粘贴?

其实我们只用 TClipboard.HasFormat 函数判断一下剪切板中是不是图片就行了.

第二版代码:

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unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Panel1: TPanel;
    Image1: TImage;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses Clipbrd;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Image1.Left := 0;
  Image1.Top := 0;
  Panel1.AutoSize := True;
  Image1.AutoSize := True;
  Image1.Picture.LoadFromFile('c:\temp\test.bmp');
  TButton(Sender).Caption := '导入';
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  {如果 Image1 还没有图片, 就别复制了, 退出吧}
  if Image1.Picture = nil then Exit;

  Clipboard.Assign(Image1.Picture);
  TButton(Sender).Caption := '复制';
end;

procedure TForm1.Button3Click(Sender: TObject);
var
  bit: TBitmap;
  x,y: Integer;
begin
  {如果当前剪切板中的东西不是图片, 就退出}
  if not Clipboard.HasFormat(CF_BITMAP) then Exit;

  bit := TBitmap.Create;
  bit.Assign(Clipboard);
  x := Panel1.Width + Panel1.Left * 2;
  y := Panel1.Top;
  Canvas.Draw(x, y, bit);
  bit.Free;
  TButton(Sender).Caption := '粘贴';
end;

end.

现在有出了新的问题: CF_BITMAP 常量表示图片, 其他格式怎么表示? 有多少格式可以用于剪切板?

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