How to read and write binary files using C++?

Methods to read and write binary files in C++: Write binary files: Use the std::ofstream class and set the output mode to std::ios::binary. Read binary files: Use the std::ifstream class and set the input mode to std::ios::binary.

How to read and write binary files in C++

A binary file is a special file type that stores non-text data, e.g. Images, Audio and Archives. There are two main operations when working with binary files in C++: reading and writing.

Writing to binary files

Use the std::ofstream class to write to binary files. When opening the file, specify the output mode as binary mode (std::ios::binary).

// 打开文件以进行二进制写入
std::ofstream outFile("binaryFile.bin", std::ios::binary);

// 向文件写入二进制数据
outFile.write((char*) &data, sizeof(data));

// 关闭文件
outFile.close();

Reading binary files

Use the std::ifstream class to read binary files. Likewise, specify binary mode when opening the file.

// 打开文件以进行二进制读取
std::ifstream inFile("binaryFile.bin", std::ios::binary);

// 从文件读取二进制数据
inFile.read((char*) &data, sizeof(data));

// 关闭文件
inFile.close();

Practical case: reading and displaying images

The following code snippet demonstrates how to read an image file in C++ and display it in the console:

#include <iostream>
#include <fstream>
#include <vector>

int main() {
  // 二进制图像文件
  std::string fileName = "image.bmp";

  // 打开图像文件以进行二进制读取
  std::ifstream inFile(fileName, std::ios::binary);

  // 检查文件是否打开
  if (!inFile.is_open()) {
    std::cerr << "无法打开文件 " << fileName << std::endl;
    return 1;
  }

  // 获取文件大小
  inFile.seekg(0, std::ios::end);
  size_t fileSize = inFile.tellg();
  inFile.seekg(0, std::ios::beg);

  // 读取图像数据
  std::vector<unsigned char> imageData(fileSize);
  inFile.read((char*) &imageData[0], fileSize);

  // 关闭文件
  inFile.close();

  // 在控制台中显示图像数据
  for (unsigned char pixel : imageData) {
    std::cout << (int)pixel << " ";
  }

  return 0;
}

This will print the value of each pixel in the image file.

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