采用Decoder:stb_image

https://github.com/nothings/stb/blob/master/stb_image.h

采用Encoder:tiny_jpeg
https://github.com/serge-rgb/TinyJPEG/blob/master/tiny_jpeg.h

stb_image.h用于解析图片格式:
JPG, PNG, TGA, BMP, PSD, GIF, HDR, PIC

tiny_jpeg.h用于保存JPG格式。

附带处理耗时计算,示例演示了一个简单的反色处理算法,并简单注释了一下部分逻辑。

完整代码:

//如果是Windows的话，调用系统API ShellExecuteA打开图片
#if defined(_MSC_VER)
#define _CRT_SECURE_NO_WARNINGS
#include <windows.h>
#define USE_SHELL_OPEN
#endif

#define STB_IMAGE_STATIC
#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"
//ref:https://github.com/nothings/stb/blob/master/stb_image.h
#define TJE_IMPLEMENTATION
#include "tiny_jpeg.h" 
//ref:https://github.com/serge-rgb/TinyJPEG/blob/master/tiny_jpeg.h
#include <math.h>
#include <io.h>
#include <iostream>
#include <string> 
#include <chrono>

//计时 
auto const epoch = std::chrono::steady_clock::now();
static double now()
{
    return std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::steady_clock::now() - epoch).count() / 1000.0;
};

template <typename FN>
static double bench(const FN &fn)
{
    auto took = -now();
    return (fn(), took + now());
}

//存储当前传入文件位置的变量
std::string m_curFilePath;

//加载图片
void loadImage(const char *filename, unsigned char *&Output, int &Width, int &Height, int &Channels)
{
    Output = stbi_load(filename, &Width, &Height, &Channels, 0);
}
//保存图片
void saveImage(const char *filename, int Width, int Height, int Channels, unsigned char *Output, bool open = true)
{
    std::string saveFile = m_curFilePath;
    saveFile += filename;
    //保存为jpg
    if (!tje_encode_to_file(saveFile.c_str(), Width, Height, Channels, Output))
    {
        fprintf(stderr, "写入 JPEG 文件失败.\n");
        return;
    }

#ifdef USE_SHELL_OPEN
    if (open)
        ShellExecuteA(NULL, "open", saveFile.c_str(), NULL, NULL, SW_SHOW);
#else
    //其他平台暂不实现
#endif
}

//取当前传入的文件位置
void getCurrentFilePath(const char *filePath, std::string &curFilePath)
{
    char drive[_MAX_DRIVE];
    char dir[_MAX_DIR];
    char fname[_MAX_FNAME];
    char ext[_MAX_EXT];
    curFilePath.clear();
    _splitpath_s(filePath, drive, dir, fname, ext);
    curFilePath += drive;
    curFilePath += dir;
    curFilePath += fname;
    curFilePath += "_";
}

//算法处理,这里以一个反色作为例子
void processImage(unsigned char *Input, unsigned char *Output, unsigned int Width, unsigned int Height, unsigned int Channels)
{
    int Stride = Width * Channels;
    if (Channels == 1)
    {
        for (unsigned int Y = 0; Y < Height; Y++)
        {
            unsigned char *scanLineOut = Output + (Y * Stride);
            unsigned char *scanLineIn = Input + (Y * Stride);
            for (unsigned int X = 0; X < Width; X++)
            {
                scanLineOut[0] = 255 - scanLineIn[0];

                scanLineIn++;
                scanLineOut++;
            }
        }
    }
    else if (Channels == 3 || Channels == 4)
    {
        for (unsigned int Y = 0; Y < Height; Y++)
        {
            unsigned char *scanLineOut = Output + (Y * Stride);
            unsigned char *scanLineIn = Input + (Y * Stride);
            for (unsigned int X = 0; X < Width; X++)
            {
                scanLineOut[0] = 255 - scanLineIn[0];
                scanLineOut[1] = 255 - scanLineIn[1];
                scanLineOut[2] = 255 - scanLineIn[2];
                //通道数为4时，不处理A通道反色(scanLineOut[3] =  255- scanLineIn[3];
                scanLineIn += Channels;
                scanLineOut += Channels;
            }
        }
    }
}

int main(int argc, char **argv)
{
    std::cout << "Image Processing " &l