C++ 读取/写入PPM图像文件C++；

尝试以我知道的唯一方式读取/写入PPM图像文件（.PPM）：

std::istream& operator >>(std::istream &inputStream, PPMObject &other)
{
    inputStream.seekg(0, ios::end);
    int size = inputStream.tellg();
    inputStream.seekg(0, ios::beg);

    other.m_Ptr = new char[size];


    while (inputStream >> other.m_Ptr >> other.width >> other.height >> other.maxColVal)
    {
        other.magicNum = (string) other.m_Ptr;
    }

    return inputStream;
}

我的值与实际文件相对应。因此，我高兴地尝试编写数据：

std::ostream& operator <<(std::ostream &outputStream, const PPMObject &other)
{
    outputStream << "P6"     << " "
        << other.width       << " "
        << other.height      << " "
        << other.maxColVal   << " "
       ;

    outputStream << other.m_Ptr;

    return outputStream;
}

基于，P6是一个二进制图像。 这将读取单个图像。请注意，不执行任何检查。这需要补充

std::istream& operator >>(std::istream &inputStream, PPMObject &other)
{
    inputStream >> other.magicNum;
    inputStream >> other.width >> other.height >> other.maxColVal;
    inputStream.get(); // skip the trailing white space
    size_t size = other.width * other.height * 3;
    other.m_Ptr = new char[size];
    inputStream.read(other.m_Ptr, size);
    return inputStream;
}

这段代码只写一个图像

std::ostream& operator <<(std::ostream &outputStream, const PPMObject &other)
{
    outputStream << "P6"     << "\n"
        << other.width       << " "
        << other.height      << "\n"
        << other.maxColVal   << "\n"
       ;
    size_t size = other.width * other.height * 3;
    outputStream.write(other.m_Ptr, size);
    return outputStream;
}

---

从inputStream提取时，不会将任何内容读入other.magicNum。它是否声明为字符串？这应该是因为我们想读“P6”。如果它是一个整数，编译器会很高兴。但是不会向成员变量中读取任何内容。这是正常的，因为文件以字符串“P6”开头。您是否显示了文件头？您的文件是否真的以“P6”开头？

std::istream& operator >>(std::istream &inputStream, PPMObject &other)
{
    inputStream >> other.magicNum;
    inputStream >> other.width >> other.height >> other.maxColVal;
    inputStream.get(); // skip the trailing white space
    size_t size = other.width * other.height * 3;
    other.m_Ptr = new char[size];
    inputStream.read(other.m_Ptr, size);
    return inputStream;
}

std::ostream& operator <<(std::ostream &outputStream, const PPMObject &other)
{
    outputStream << "P6"     << "\n"
        << other.width       << " "
        << other.height      << "\n"
        << other.maxColVal   << "\n"
       ;
    size_t size = other.width * other.height * 3;
    outputStream.write(other.m_Ptr, size);
    return outputStream;
}

struct PPMObject
{
  std::string magicNum;
  int width, height, maxColVal;
  char * m_Ptr;
};