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库来绘制直角坐标系，并将坐标原点放置在窗口的中心。以下是一个简单的示例代码：

#include <Windows.h>

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, 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 = WndProc;
    wc.hInstance = hInstance;
    wc.lpszClassName = CLASS_NAME;

    RegisterClass(&wc);

    HWND hwnd = CreateWindowEx(
        0,
        CLASS_NAME,
        L"Sample Window",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
        NULL,
        NULL,
        hInstance,
        NULL
    );

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

    ShowWindow(hwnd, nCmdShow);

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

    return 0;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
    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;

        // 将坐标原点移动到窗口中心
        int originX = width / 2;
        int originY = height / 2;

        // 绘制直角坐标系
        SelectObject(hdc, GetStockObject(DC_PEN));
        SetDCPenColor(hdc, RGB(0, 0, 0));

        MoveToEx(hdc, 0, originY, NULL);
        LineTo(hdc, width, originY);

        MoveToEx(hdc, originX, 0, NULL);
        LineTo(hdc, originX, height);

        // 绘制刻度
        SelectObject(hdc, GetStockObject(DC_BRUSH));
        SetDCBrushColor(hdc, RGB(0, 0, 0));

        int scaleLength = 10; // 刻度的长度
        int scaleInterval = 50; // 刻度之间的间隔

        // 绘制X轴刻度
        for (int x = originX + scaleInterval; x < width; x += scaleInterval)
        {
            Rectangle(hdc, x, originY - scaleLength / 2, x + 1, originY + scaleLength / 2);
        }

        for (int x = originX - scaleInterval; x > 0; x -= scaleInterval)
        {
            Rectangle(hdc, x, originY - scaleLength / 2, x + 1, originY + scaleLength / 2);
        }

        // 绘制Y轴刻度
        for (int y = originY + scaleInterval; y < height; y += scaleInterval)
        {
            Rectangle(hdc, originX - scaleLength / 2, y, originX + scaleLength / 2, y + 1);
        }

        for (int y = originY - scaleInterval; y > 0; y -= scaleInterval)
        {
            Rectangle(hdc, originX - scaleLength / 2, y, originX + scaleLength / 2, y + 1);
        }

        EndPaint(hwnd, &ps);
        break;
    }
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hwnd, msg, wParam, lParam);
    }

    return 0;
}

这段代码会创建一个简单的窗口，并在窗口的`WM_PAINT`消息处理函数中绘制直角坐标系和刻度。您可以将该代码保存为一个.cpp文件，然后使用Visual Studio等编译器进行编译运行。窗口会显示一个带有直角坐标系和刻度的画布。

请注意，这只是一个简单的示例，绘制的直角坐标系和刻度可能不是非常准确和完整，您可以根据自己的需求进行修改和扩展。