c++将jpg转换为灰度图
step1:添加依赖
下载这两个文件，放在cpp同一目录下，编译生成
https://github.com/nothings/stb/blob/master/stb_image_write.h
https://github.com/nothings/stb/blob/master/stb_image.h
step2:C:\Users\wangrusheng\source\repos\CMakeProject1\CMakeProject1\CMakeProject1.cpp
#include <vector>
#include <string>
#include <iostream>// 必须在使用前定义这些宏
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h" // 图像加载库
#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image_write.h" // 图像保存库void convert_to_grayscale(const std::string& input_path,const std::string& output_path,int quality = 75)
{// 加载原始图像int width, height, channels;unsigned char* orig_data = stbi_load(input_path.c_str(), &width, &height, &channels, 0);if (!orig_data) {std::cerr << "错误：无法加载图像 " << input_path<< "\n原因: " << stbi_failure_reason() << std::endl;return;}std::cout << "已加载图像: " << width << "x" << height<< "，通道数: " << channels << std::endl;// 创建灰度数据缓冲区（单通道）std::vector<unsigned char> gray_data(width * height);// 灰度转换核心算法const float R_WEIGHT = 0.299f;const float G_WEIGHT = 0.587f;const float B_WEIGHT = 0.114f;for (int y = 0; y < height; ++y) {for (int x = 0; x < width; ++x) {// 计算当前像素的内存位置const int pixel_index = (y * width + x) * channels;// 获取RGB分量（自动兼容3/4通道图像）unsigned char r = orig_data[pixel_index];unsigned char g = orig_data[pixel_index + 1];unsigned char b = orig_data[pixel_index + 2];// 计算灰度值（加权平均法）gray_data[y * width + x] = static_cast<unsigned char>(R_WEIGHT * r +G_WEIGHT * g +B_WEIGHT * b);}}// 保存灰度图像（JPEG格式）if (!stbi_write_jpg(output_path.c_str(), width, height, 1, gray_data.data(), quality)) {std::cerr << "错误：无法保存图像到 " << output_path << std::endl;}// 释放原始图像内存stbi_image_free(orig_data);
}int main() {// 输入输出路径（使用原始字符串避免转义）const std::string input_file = R"(C:\Users\wangrusheng\Downloads\red.jpg)";const std::string output_file = R"(C:\Users\wangrusheng\Downloads\new_gray.jpg)";// 执行转换并设置JPEG质量为85%convert_to_grayscale(input_file, output_file, 85);std::cout << "转换完成，请检查输出文件: " << output_file << std::endl;return 0;
}
end
)
