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我编写了一个简单的 C++ 类程序来读取和/或打印一些 BMP 头信息，如下所示，它工作得很好。但是，我想利用 C++ 构造函数初始化程序可以提供的优势。因此，我想使用 C++ 构造函数初始化程序来打开文件并检索数据，即 mOffBits、mWidth 和 mHeight。这可能吗？

头文件：

#include <fstream>
#include <iostream>
#include <string>

class BMP
{
  public:
        BMP (const std::string& inFileName);
        ~BMP ();
        const void printInfo () const;

  private:
        std::ifstream ifs;
        std::string mInFileName;
        std::uint32_t mOffBits;
        std::int32_t mWidth, mHeight;
        char str [54];
};

程序文件：

#include "bmp.h"

BMP::BMP (const std::string& inFileName) : mInFileName (inFileName)
{
        ifs.open (mInFileName, std::ios::in | std::ios::binary);

        ifs.seekg (0, std::ios::beg);
        ifs.read (&str [0], 54);
        mOffBits = *reinterpret_cast <std::uint32_t*> (&str [0xA]);
        mWidth = *reinterpret_cast <std::int32_t*> (&str [0x12]);
        mHeight = *reinterpret_cast <std::int32_t*> (&str [0x16]);
}


BMP::~BMP ()
{
        ifs.close ();
}


const void BMP::printInfo () const
{
        std::cout << "\tInput filename:\t\t" << mInFileName << std::endl;
        std::cout << "\tBegin of IMG data:\t" << mOffBits << std::endl;
        std::cout << "\tHeight:\t\t\t" << mHeight << std::endl;
        std::cout << "\tWidth:\t\t\t" << mWidth << std::endl;
}

主.cpp：

#include "bmp.h"

auto main (int argc, char* argv []) -> int
{
        if (argc < 2)
        {
                std::cout << argv [0] << " image.bmp" << std::endl;
                return 1;
        }

        // Itialize bmp class;
        BMP bmp (argv [1]);

        // print out header information.
        bmp.printInfo ();

        return 0;
}
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