using namespace std;

#include <iostream>
#include <cmath>
#include "lodepng.h"

int main(int argc, char *argv[]) {

    std::vector<unsigned char> pixels; //the raw pixels
    unsigned width, height;

    //load and decode
    lodepng::decode(pixels, width, height, "in.png");


    //increase brightness
    unsigned char image[width * height * 3];
    for(unsigned y = 0; y < height; y++)
        for(unsigned x = 0; x < width; x++) {
            size_t byte_index = (y * width + x)  * 3;
            image[byte_index] = (unsigned char)min(255, pixels[byte_index] + 30);
            image[byte_index + 1] = (unsigned char)min(255, pixels[byte_index + 1] + 30);
            image[byte_index + 2] = (unsigned char)min(255, pixels[byte_index + 2] + 30);
        }

    //encode and save
    lodepng::encode("out.png", image, width, height);
}