Read and write png files bytes by bytes

#include 
#include 
#include 

#define WIDTH  (3)
#define HEIGHT (3)

int main()
{
    unsigned char   **image;                                // image[HEIGHT][WIDTH]の形式です
    int             i, j;

    image = (png_bytepp)malloc(HEIGHT * sizeof(png_bytep)); // 以下３行は２次元配列を確保します
    for (j = 0; j < HEIGHT; j++)
            image[j] = (png_bytep)malloc(WIDTH * sizeof(png_byte));


    for (i = 0; i < WIDTH; i++) {                           // 以下５行は単純なテストパターンを作ります
            for (j = 0; j < HEIGHT; j++) {
                    image[j][i] = (unsigned char)i;
            }
    }


    unsigned char *image2;

    image2 = (png_bytep) malloc( HEIGHT * WIDTH * sizeof(png_byte));

    for (i = 0; i < WIDTH; i++) {                           // 以下５行は単純なテストパターンを作ります
            for (j = 0; j < HEIGHT; j++) {
                    //printf("%d ", image[j][i]);
                    image2[j * WIDTH + i] = image[j][i];
                    printf("%d ", image2[j * WIDTH + i]);

            }
    }
    // TODO: write image2 to png stream
    // http://www.jah.ne.jp/~naoyuki/Writings/MngPng.html
    return 0;
}