如何获取显示器的正确物理尺寸? [英] How to obtain the correct physical size of the monitor?

问题描述

如何获得以厘米或英寸为单位的显示器尺寸?

How can I get the size of the display in centimeters or inches?

此代码并不总是正常工作:

This code does not always works correctly:

HDC hdc = CreateDC(_T("DISPLAY"),dd.DeviceName,NULL,NULL);
int width = GetDeviceCaps(hdc, HORZSIZE);
int height = GetDeviceCaps(hdc, VERTSIZE);
ReleaseDC(0, hdc)

特别适用于多显示器配置.

Especially for multi-monitor configuration.

更新:我需要获取普通显示器的尺寸，这些显示器具有恒定的物理尺寸.

Update: I need to get the size just for ordinary monitors, which have a constant physical size.

推荐答案

我找到了另一种方法.显示器的物理大小存储在 EDID 中，Windows 几乎总是注册表中其值的副本.如果你能解析EDID，你就可以以厘米为单位读取显示器的宽度和高度.

I found another way. The physical size of the monitor are stored in the EDID, and Windows are almost always copies of its value in the registry. If you can parse EDID, you can read the width and height of the monitor in centimeters.

更新:添加代码

BOOL GetMonitorDevice( TCHAR* adapterName, DISPLAY_DEVICE &ddMon )
{
    DWORD devMon = 0;

    while (EnumDisplayDevices(adapterName, devMon, &ddMon, 0))
    {
        if (ddMon.StateFlags & DISPLAY_DEVICE_ACTIVE &&
            ddMon.StateFlags & DISPLAY_DEVICE_ATTACHED) // for ATI, Windows XP
            break;

        devMon++;
    }

    if (ddMon.DeviceString[0] == '')
    {
        EnumDisplayDevices(adapterName, 0, &ddMon, 0);
        if (ddMon.DeviceString[0] == '')
            _tcscpy_s(ddMon.DeviceString, _T("Default Monitor"));
    }
    return ddMon.DeviceID[0] != '';
}

BOOL GetMonitorSizeFromEDID(TCHAR* adapterName, DWORD& Width, DWORD& Height)
{
    DISPLAY_DEVICE ddMon;
    ZeroMemory(&ddMon, sizeof(ddMon));
    ddMon.cb = sizeof(ddMon);

    //read edid
    bool result = false;
    Width = 0;
    Height = 0;
    if (GetMonitorDevice(adapterName, ddMon))
    {
        TCHAR model[8];
        TCHAR* s = _tcschr(ddMon.DeviceID, '\') + 1;
        size_t len = _tcschr(s, '\') - s;
        if (len >= _countof(model))
            len = _countof(model) - 1;
        _tcsncpy_s(model, s, len);

        TCHAR *path = _tcschr(ddMon.DeviceID, '\') + 1;
        TCHAR str[MAX_PATH] = _T("SYSTEM\CurrentControlSet\Enum\DISPLAY\");
        _tcsncat_s(str, path, _tcschr(path, '\')-path);
        path = _tcschr(path, '\') + 1;
        HKEY hKey;
        if(RegOpenKeyEx(HKEY_LOCAL_MACHINE, str, 0, KEY_READ, &hKey) == ERROR_SUCCESS)
        {
            DWORD i = 0;
            DWORD size = MAX_PATH;
            FILETIME ft;
            while(RegEnumKeyEx(hKey, i, str, &size, NULL, NULL, NULL, &ft) == ERROR_SUCCESS)
            {
                HKEY hKey2;
                if(RegOpenKeyEx(hKey, str, 0, KEY_READ, &hKey2) == ERROR_SUCCESS)
                {
                    size = MAX_PATH;
                    if(RegQueryValueEx(hKey2, _T("Driver"), NULL, NULL, (LPBYTE)&str, &size) == ERROR_SUCCESS)
                    {
                        if (_tcscmp(str, path) == 0)
                        {
                            HKEY hKey3;
                            if(RegOpenKeyEx(hKey2, _T("Device Parameters"), 0, KEY_READ, &hKey3) == ERROR_SUCCESS)
                            {
                                BYTE EDID[256];
                                size = 256;
                                if(RegQueryValueEx(hKey3, _T("EDID"), NULL, NULL, (LPBYTE)&EDID, &size) == ERROR_SUCCESS)
                                {
                                    DWORD p = 8;
                                    TCHAR model2[9];

                                    char byte1 = EDID[p];
                                    char byte2 = EDID[p+1];
                                    model2[0]=((byte1 & 0x7C) >> 2) + 64;
                                    model2[1]=((byte1 & 3) << 3) + ((byte2 & 0xE0) >> 5) + 64;
                                    model2[2]=(byte2 & 0x1F) + 64;
                                    _stprintf(model2 + 3, _T("%X%X%X%X"), (EDID[p+3] & 0xf0) >> 4, EDID[p+3] & 0xf, (EDID[p+2] & 0xf0) >> 4, EDID[p+2] & 0x0f);
                                    if (_tcscmp(model, model2) == 0)
                                    {
                                        Width = EDID[22];
                                        Height = EDID[21];
                                        result = true;
                                    }
                                    else
                                    {
                                        // EDID incorrect
                                    }
                                }
                                RegCloseKey(hKey3);
                            }
                        }
                    }
                    RegCloseKey(hKey2);
                }
                i++;
            }
            RegCloseKey(hKey);
        }
    }

    return result;
}

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