藉助影象庫stb_image實現讀取、儲存PNG。

stb下載:https://files-cdn.cnblogs.com/files/Kingfans/stb.zip

#include <string>

#define STB_IMAGE_IMPLEMENTATION
#include "stb/stb_image.h"

#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb/stb_image_write.h"

void ColorToGrey(std::string strColorPath, std::string strGreyPath)
{
    
 
int iWidth, iHeight, iTunnel;
    unsigned char *data = stbi_load(strColorPath.c_str(), &iWidth, &iHeight, &iTunnel, 0);

    //change pixel
    switch (iTunnel)
    {
    case 3:
        {
            for (int dx = 0; dx < iWidth*iHeight; dx++)
            {
                unsigned char
 
 iRed = data[3 * dx];
                unsigned char iGreen = data[3 * dx + 1];
                unsigned char iBlue = data[3 * dx + 2];

                unsigned char iGray = 0.3*iRed + 0.59*iGreen + 0.11*iBlue;
                data[3 * dx] = iGray;
                data[3 * dx + 1] = iGray;
                data[
 
3 * dx + 2] = iGray;
            }
        }
        break;
    case 4:
        {
            for (int dx = 0; dx < iWidth*iHeight; dx++)
            {
                unsigned char iRed = data[4 * dx];
                unsigned char iGreen = data[4 * dx + 1];
                unsigned char iBlue = data[4 * dx + 2];
                unsigned char iAlpha = data[4 * dx + 3];

                unsigned char iGray = 0.3*iRed + 0.59*iGreen + 0.11*iBlue;
                data[4 * dx] = iGray;
                data[4 * dx + 1] = iGray;
                data[4 * dx + 2] = iGray;
                data[4 * dx + 3] = 255;
            }
        }
        break;
    default:
        break;
    }
    stbi_write_png(strGreyPath.c_str(), iWidth, iHeight, iTunnel, data, iWidth * iTunnel);
    stbi_image_free(data);
}

int main()
{
    ColorToGrey("E://1_color.png", "E://1_grey.png");

    return 0;
}

實現效果：