编程绘制函数和坐标系 c 语言

以下是一个简单的示例程序，用于在屏幕上绘制一个函数和坐标系。该程序使用了 Windows API 来绘制图形。

#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)
{
    WNDCLASSEX wc;
    HWND hwnd;
    MSG Msg;

    // 注册窗口类
    wc.cbSize = sizeof(WNDCLASSEX);
    wc.style = 0;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = "MyClass";
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

    if (!RegisterClassEx(&wc))
    {
        MessageBox(NULL, "Window Registration Failed!", "Error", MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    // 创建窗口
    hwnd = CreateWindowEx(
        WS_EX_CLIENTEDGE,
        "MyClass",
        "My Window",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 640, 480,
        NULL, NULL, hInstance, NULL);

    if (hwnd == NULL)
    {
        MessageBox(NULL, "Window Creation Failed!", "Error", MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    ShowWindow(hwnd, nCmdShow);
    UpdateWindow(hwnd);

    // 消息循环
    while (GetMessage(&Msg, NULL, 0, 0) > 0)
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }

    return Msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    HDC hdc;
    PAINTSTRUCT ps;
    static int xMin = -10, xMax = 10, yMin = -10, yMax = 10;
    static int xOrigin, yOrigin, xScale, yScale;

    switch (msg)
    {
    case WM_CREATE:
        // 设置坐标系原点和比例
        xOrigin = 50;
        yOrigin = 430;
        xScale = 30;
        yScale = 30;
        break;

    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);

        // 绘制坐标系
        MoveToEx(hdc, xOrigin, yOrigin, NULL);
        LineTo(hdc, xOrigin + (xMax - xMin) * xScale, yOrigin);
        MoveToEx(hdc, xOrigin, yOrigin, NULL);
        LineTo(hdc, xOrigin, yOrigin - (yMax - yMin) * yScale);

        // 绘制函数 y = sin(x)
        int x, y;
        double dx = 0.1;
        for (double i = xMin; i <= xMax; i += dx)
        {
            x = xOrigin + (i - xMin) * xScale;
            y = yOrigin - sin(i) * yScale;
            SetPixel(hdc, x, y, RGB(255, 0, 0));
        }

        EndPaint(hwnd, &ps);
        break;

    case WM_DESTROY:
        PostQuitMessage(0);
        break;

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

    return 0;
}

该程序绘制了 $y=\sin(x)$ 函数和坐标系，如下图所示：