屏幕相关操作（XE10.1+WIN8.164）

相关资料：

http://www.bianceng.cn/Programming/Delphi/201104/25455.htm

http://blog.csdn.net/anbangs/article/details/5008923

http://bbs.csdn.net/topics/280065261?locationNum=11

注意事项：

1.改屏幕分辨率时，不是随意的，如果显示器不支持的话，只能右击属性里面看一下支持哪些分辨率。

实例代码：

 unit Unit1;

 interface

 uses
   Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
   Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ExtCtrls,
   Vcl.Imaging.jpeg;

 type
   TForm1 = class(TForm)
     Button2: TButton;
     Button3: TButton;
     Button4: TButton;
     Label1: TLabel;
     Label2: TLabel;
     Label3: TLabel;
     Button1: TButton;
     Image1: TImage;
     procedure Button2Click(Sender: TObject);
     procedure Button3Click(Sender: TObject);
     procedure Button4Click(Sender: TObject);
     procedure Button1Click(Sender: TObject);
   private
     { Private declarations }
   public
     { Public declarations }
   end;

 var
   Form1: TForm1;

 implementation

 {$R *.dfm}

 procedure TForm1.Button1Click(Sender: TObject);
 var
   mmW,mmH: Integer;
   pixW,pixH: Integer;
   pm: Double;
 begin
   {以毫米为单位获取屏幕尺寸}
   mmW := GetDeviceCaps(Canvas.Handle, HORZSIZE);
   mmH := GetDeviceCaps(Canvas.Handle, VERTSIZE);
   ShowMessageFmt('屏幕宽: %d 毫米; 屏幕高: %d 毫米', [mmW, mmH]);
   {屏幕宽: 510 毫米; 屏幕高: 287 毫米}
   {以像素为单位获取屏幕尺寸}
   pixW := GetDeviceCaps(Canvas.Handle, HORZRES);
   pixH := GetDeviceCaps(Canvas.Handle, VERTRES);
   ShowMessageFmt('屏幕宽: %d 像素; 屏幕高: %d 像素', [pixW, pixH]);
   {屏幕宽: 1920 像素; 屏幕高: 1080 像素}
   {当前状态下, 1 毫米等于多少像素?}
   ShowMessage(FloatToStr(pixW / mmW)); {3.76470588235294}
   ShowMessage(FloatToStr(pixH / mmH)); {3.76306620209059}
   {一步获取}
   pm := GetDeviceCaps(Canvas.Handle, HORZRES) / GetDeviceCaps(Canvas.Handle, HORZSIZE);
   ShowMessage(FloatToStr(pm)); {3.76470588235294}
 end;

 procedure TForm1.Button2Click(Sender: TObject);
 var
   lpDevMode: TDeviceMode;
 begin
   EnumDisplaySettings(nil, , lpDevMode);
   lpDevMode.dmFields := DM_PELSWIDTH or DM_PELSHEIGHT;
   lpDevMode.dmPelsWidth := ;
   lpDevMode.dmPelsHeight := ;
   ChangeDisplaySettings(lpDevMode, );
 end;

 procedure TForm1.Button3Click(Sender: TObject);
 begin
   Label1.Caption := IntToStr(screen.width);//宽
   Label2.Caption := IntToStr(screen.height);//高
   Label3.Caption := IntToStr(Screen.MonitorCount);//显示器数量
 end;

 procedure TForm1.Button4Click(Sender: TObject);
 begin
   //我的电脑最大支持1920，所以返回的是1920
   case GetDeviceCaps(GetDC(Form1.Handle), HORZRES) of
     : //对640×480分辨率进行处理的代码；
     begin
     end;
     : //对800×600分辨率进行处理的代码；
     begin
     end;
     : //对1024×768分辨率进行处理的代码；
     begin
     end;
     : //对1280×1024分辨率进行处理的代码；
     begin
     end;
     ://1600*900
     begin
     end;
     ://1920*1080
     begin
     end;
   end;
 end;

 end.