请使用C语言，写出一个使用Windows自带函数的，能够导入外部图片的代码，并且有注释

好的，以下是一个使用C语言和Windows自带函数的示例代码，可以导入外部图片：

#include <windows.h>
#include <wingdi.h>

int main()
{
    // 打开文件对话框，选择图片文件
    OPENFILENAME ofn;
    char szFileName[MAX_PATH] = { 0 };
    ZeroMemory(&ofn, sizeof(ofn));
    ofn.lStructSize = sizeof(ofn);
    ofn.hwndOwner = NULL;
    ofn.lpstrFilter = "Image Files (*.bmp;*.jpg;*.png)\0*.bmp;*.jpg;*.png\0All Files (*.*)\0*.*\0";
    ofn.lpstrFile = szFileName;
    ofn.nMaxFile = MAX_PATH;
    ofn.Flags = OFN_EXPLORER | OFN_FILEMUSTEXIST | OFN_HIDEREADONLY;
    ofn.lpstrDefExt = "";

    if (GetOpenFileName(&ofn))
    {
        // 打开图片文件，读取数据
        HANDLE hFile = CreateFile(ofn.lpstrFile, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
        if (hFile != INVALID_HANDLE_VALUE)
        {
            DWORD dwFileSize = GetFileSize(hFile, NULL);
            BYTE* pbFileData = (BYTE*)malloc(dwFileSize);
            DWORD dwBytesRead = 0;
            ReadFile(hFile, pbFileData, dwFileSize, &dwBytesRead, NULL);

            // 创建位图
            BITMAPINFO bmpInfo;
            ZeroMemory(&bmpInfo, sizeof(bmpInfo));
            bmpInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
            bmpInfo.bmiHeader.biWidth = 0;   // 宽度和高度为0时，CreateDIBSection会根据文件数据自动计算
            bmpInfo.bmiHeader.biHeight = 0;
            bmpInfo.bmiHeader.biPlanes = 1;
            bmpInfo.bmiHeader.biBitCount = 0;
            bmpInfo.bmiHeader.biCompression = BI_RGB;
            bmpInfo.bmiHeader.biSizeImage = 0;
            bmpInfo.bmiHeader.biXPelsPerMeter = 0;
            bmpInfo.bmiHeader.biYPelsPerMeter = 0;
            bmpInfo.bmiHeader.biClrUsed = 0;
            bmpInfo.bmiHeader.biClrImportant = 0;

            BITMAPINFOHEADER* pHeader = &bmpInfo.bmiHeader;
            if (pbFileData[0] == 'B' && pbFileData[1] == 'M')
            {
                // bmp格式
                pHeader = (BITMAPINFOHEADER*)(pbFileData + 14);
            }
            else if (pbFileData[0] == 0xFF && pbFileData[1] == 0xD8)
            {
                // jpg格式
                BYTE* pStart = pbFileData;
                BYTE* pEnd = pbFileData + dwFileSize;
                while (pStart < pEnd)
                {
                    if (pStart[0] == 0xFF && pStart[1] == 0xC0)
                    {
                        pHeader = (BITMAPINFOHEADER*)(pStart + 2);
                        break;
                    }
                    pStart++;
                }
            }
            else if (pbFileData[0] == 0x89 && pbFileData[1] == 'P' && pbFileData[2] == 'N' && pbFileData[3] == 'G')
            {
                // png格式
                pHeader = (BITMAPINFOHEADER*)(pbFileData + 16);
            }

            // 创建设备无关位图
            HDC hdc = GetDC(NULL);
            HBITMAP hBitmap = CreateDIBSection(hdc, &bmpInfo, DIB_RGB_COLORS, NULL, NULL, 0);
            ReleaseDC(NULL, hdc);

            // 复制数据到位图
            BYTE* pBits = NULL;
            HDC hMemDC = CreateCompatibleDC(NULL);
            HBITMAP hOldBitmap = (HBITMAP)SelectObject(hMemDC, hBitmap);
            SetDIBits(hMemDC, hBitmap, 0, pHeader->biHeight, pbFileData + pHeader->biSize, &bmpInfo, DIB_RGB_COLORS);

            // 保存位图为文件
            HANDLE hFileOut = CreateFile("output.bmp", GENERIC_WRITE, FILE_SHARE_WRITE, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
            if (hFileOut != INVALID_HANDLE_VALUE)
            {
                BITMAPFILEHEADER fileHeader;
                ZeroMemory(&fileHeader, sizeof(fileHeader));
                fileHeader.bfType = 0x4D42;
                fileHeader.bfSize = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER) + pHeader->biSizeImage;
                fileHeader.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
                DWORD dwBytesWritten = 0;
                WriteFile(hFileOut, &fileHeader, sizeof(fileHeader), &dwBytesWritten, NULL);
                WriteFile(hFileOut, pHeader, sizeof(BITMAPINFOHEADER), &dwBytesWritten, NULL);
                WriteFile(hFileOut, pbFileData + pHeader->biSize, pHeader->biSizeImage, &dwBytesWritten, NULL);
                CloseHandle(hFileOut);
            }

            // 释放资源
            SelectObject(hMemDC, hOldBitmap);
            DeleteDC(hMemDC);
            free(pbFileData);
            DeleteObject(hBitmap);
        }
        CloseHandle(hFile);
    }

    return 0;
}

以上代码通过Windows自带的GetOpenFileName函数打开文件对话框，选择图片文件，然后使用CreateFile函数打开图片文件，读取数据。接着创建位图，根据文件数据自动计算宽度和高度，使用CreateDIBSection函数创建设备无关位图，并将数据复制到位图中。最后将位图保存为文件，释放资源。需要注意的是，以上代码只支持bmp、jpg和png格式的图片。