1、获取屏幕分辨率

1.1 GetSystemMetrics

整个屏幕区域。

# include <windows.h>
int cx = GetSystemMetrics( SM_CXSCREEN );   
int cy = GetSystemMetrics( SM_CYSCREEN );

不包括任务栏等区域.

# include <windows.h>
int cx = GetSystemMetrics( SM_CXFULLSCREEN );
int cy = GetSystemMetrics( SM_CYFULLSCREEN );

1.2 GetDeviceCaps

HDC hDC = ::GetDC(NULL);               // 得到屏幕DC  
int cx = ::GetDeviceCaps(hDC,HORZRES);       // 宽  
int cy = ::GetDeviceCaps(hDC,VERTRES);        // 高   
::ReleaseDC(NULL,hDC);                  // 释放DC

HDC hDC = ::GetDC(NULL);               // 得到屏幕DC  
int cx = ::GetDeviceCaps(hDC,DESKTOPHORZRES);       // 宽  
int cy = ::GetDeviceCaps(hDC,DESKTOPVERTRES);        // 高   
::ReleaseDC(NULL,hDC);                  // 释放DC

1.3 SystemParametersInfo

RECT rect;
SystemParametersInfo(SPI_GETWORKAREA, 0, &rect, SPIF_SENDCHANGE);
int cx = (rect.right - rect.left);
int cy = (rect.bottom - rect.top);

1.4 GetDesktopWindow

HWND hd = GetDesktopWindow();
RECT rect;
GetWindowRect(hd, &rect);
int cx = (rect.right - rect.left);
int cy = (rect.bottom - rect.top);

2、获取屏幕显示比例

GetDpiForWindow function (winuser.h)
Minimum supported client Windows 10, version 1607 [desktop apps only]

DPI 的基值定义为 USER _ DEFAULT SCREEN _ _ DPI，设置为 96。若要确定监视器的缩放因子，请取 DPI 值并除以 USER _ DEFAULT SCREEN _ _ DPI。下表提供了一些示例 DPI 值和相关缩放因子。

DPI 值	缩放百分比
96	100%
120	125%
144	150%
192	200%

#include <Windows.h>
#include <iostream>

HWND hd = GetDesktopWindow();
int zoom = GetDpiForWindow(hd);
double dpi = 0;

switch (zoom) {
case 96:
	dpi = 1;
	std::cout << "100%" << std::endl;
	break;
case 120:
	dpi = 1.25;
	std::cout << "125%" << std::endl;
	break;
case 144:
	dpi = 1.5;
	std::cout << "150%" << std::endl;
	break;
case 192:
	dpi = 2;
	std::cout << "200%" << std::endl;
	break;
default:
	std::cout << "error" << std::endl;
	break;
}