// перенос пикселя при создании коллажа
void replace(png_byte *new_pixel, png_byte *old_pixel, int width_pixel) {
    for (int i = 0; i < width_pixel; i++) {
        new_pixel[i] = old_pixel[i];
    }
}

void make_collage(struct Png *image, int width_pixel, int x_photos, int y_photos) {
    int new_width = image->width * x_photos;
    int new_height = image->height * y_photos;

    png_byte **new_mas = (png_byte **) malloc(sizeof(png_byte * ) * new_height);
    for (int y = 0; y < new_height; y++)
        new_mas[y] = (png_byte *) malloc(sizeof(png_byte) * new_width * width_pixel);
    for (int y = 0; y < new_height; y++) {
        int old_y = y % image->height;
        png_byte *old_row = image->row_pointers[old_y];
        png_byte *new_row = new_mas[y];
        for (int x = 0; x < new_width; x++) {
            int old_x = x % image->width;
            png_byte *old_pixel = &(old_row[old_x * width_pixel]);
            png_byte *new_pixel = &(new_row[x * width_pixel]);
            replace(new_pixel, old_pixel, width_pixel);
        }
    }
    for (int x = 0; x < image->height; x++) {
        free(image->row_pointers[x]);
    }
    free(image->row_pointers);

    image->row_pointers = new_mas;
    image->width = new_width;
    image->height = new_height;
}