#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image_write.h"

FILE *fd;
size_t file_sz;
unsigned char *file_cnt, *canvas;
char *filename_output;

int main(int argc, char *argv[])
{
	argv++;
	while(--argc){

		const char* filename = *argv++;
		filename_output = malloc(sizeof(char) * strlen(filename) + 8);
		strcpy(filename_output, filename);
		fd = fopen(filename, "r");
		if(fd == NULL){
			fprintf(stderr, "couldn't open this file: %s\n", filename);
			continue;
		}

		// get file size
		fseek(fd, 0, SEEK_END);
		file_sz = ftell(fd);
		rewind(fd);
		
		file_cnt = malloc(sizeof(char)*file_sz);
		fread(file_cnt, sizeof(char), file_sz, fd);

		canvas = calloc(256*256, sizeof(char));

		double weight = (double)file_sz / 255; 

		for (size_t i = 0; i < file_sz - 1; ++i) {
			unsigned char at_pos = file_cnt[i], next_pos = file_cnt[i+1];
			canvas[at_pos + next_pos * 256] += weight;
		}

		stbi_write_png(strcat(filename_output, ".out.png"), 256, 256, 1, canvas, 256);

		free(canvas);
		free(file_cnt);
		free(filename_output);
		fclose(fd);
	}
	return 0;
}