C++GDI绘制直角坐标系，坐标原点在窗口中心，并绘制刻度

您可以使用C++的GDI（图形设备接口）来绘制直角坐标系并将坐标原点放在窗口中心。以下是一个简单的示例代码：

#include <windows.h>

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    // 创建窗口
    const wchar_t CLASS_NAME[] = L"Sample Window Class";
    WNDCLASS wc = {};

    wc.lpfnWndProc = WindowProc;
    wc.hInstance = hInstance;
    wc.lpszClassName = CLASS_NAME;

    RegisterClass(&wc);

    HWND hwnd = CreateWindowEx(
        0,
        CLASS_NAME,
        L"DirectDraw Sample",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        800,
        600,
        nullptr,
        nullptr,
        hInstance,
        nullptr
    );

    if (hwnd == nullptr)
    {
        return 0;
    }

    ShowWindow(hwnd, nCmdShow);

    // 消息循环
    MSG msg = {};
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return 0;
}

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch (uMsg)
    {
    case WM_PAINT:
    {
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hwnd, &ps);

        // 获取窗口尺寸
        RECT rect;
        GetClientRect(hwnd, &rect);
        int width = rect.right - rect.left;
        int height = rect.bottom - rect.top;

        // 设置坐标原点在窗口中心
        SetViewportOrgEx(hdc, width / 2, height / 2, nullptr);

        // 绘制直角坐标系
        MoveToEx(hdc, -width / 2, 0, nullptr);
        LineTo(hdc, width / 2, 0);
        MoveToEx(hdc, 0, -height / 2, nullptr);
        LineTo(hdc, 0, height / 2);

        // 绘制刻度
        const int scaleLength = 10; // 刻度长度
        const int scaleInterval = 50; // 刻度间隔

        for (int x = -width / 2 + scaleInterval; x < width / 2; x += scaleInterval)
        {
            MoveToEx(hdc, x, -scaleLength, nullptr);
            LineTo(hdc, x, scaleLength);
        }

        for (int y = -height / 2 + scaleInterval; y < height / 2; y += scaleInterval)
        {
            MoveToEx(hdc, -scaleLength, y, nullptr);
            LineTo(hdc, scaleLength, y);
        }

        EndPaint(hwnd, &ps);
    }
    return 0;

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;

    default:
        return DefWindowProc(hwnd, uMsg, wParam, lParam);
    }
}

这段代码创建了一个窗口，并在窗口中心绘制了直角坐标系和刻度。您可以将该代码保存为.cpp文件，并使用Visual Studio等编译器进行编译运行。