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, 0, lpDevMode);
  lpDevMode.dmFields := DM_PELSWIDTH or DM_PELSHEIGHT;
  lpDevMode.dmPelsWidth := 1600;
  lpDevMode.dmPelsHeight := 900;
  ChangeDisplaySettings(lpDevMode, 0);
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
    640: //对640×480分辨率进行处理的代码；
    begin
    end;
    800: //对800×600分辨率进行处理的代码；
    begin
    end;
    1024: //对1024×768分辨率进行处理的代码；
    begin
    end;
    1280: //对1280×1024分辨率进行处理的代码；
    begin
    end;
    1600://1600*900
    begin
    end;
    1920://1920*1080
    begin
    end;
  end;
end;

end.