#include <stdio.h>
#include <stdlib.h>
#include <png.h>

#define WIDTH 256
#define HEIGHT 256

int main (int argc, char** argv) {
	png_structp png_ptr;
	png_infop png_info;
	png_byte** image;
	unsigned i;
	unsigned x, y;
	unsigned char s1, s2;
	unsigned intensity;

	if (argc > 1)
		intensity = atoi (argv[1]);
	else
		intensity = 1;

	png_ptr = png_create_write_struct (PNG_LIBPNG_VER_STRING,
			NULL, NULL, NULL);
	png_info = png_create_info_struct (png_ptr);
	png_init_io (png_ptr, stdout);

	png_set_IHDR (png_ptr, png_info, WIDTH, HEIGHT, 16, PNG_COLOR_TYPE_RGB,
			PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

	image = malloc (sizeof (png_bytep) * HEIGHT);
	for (i = 0; i < HEIGHT; ++i) {
		image[i] = malloc (sizeof (png_byte) * WIDTH * 6);
	}

	// Max out all alpha channels
	for (y = 0; y < HEIGHT; ++y) {
		for (x = 0; x < WIDTH; ++x) {
			image[y][x*6+1] = 255;
			image[y][x*6+3] = 255;
			image[y][x*6+5] = 255;
		}
	}

	s1 = fgetc (stdin);
	while (!feof (stdin)) {
		s2 = s1;
		s1 = fgetc (stdin);

		image[s1][s2*6] = image[s1][s2*6+2] = image[s1][s2*6+4] =
			image[s1][s2*6] + intensity > 255 ? 255 : image[s1][s2*6] + intensity;
	}

	png_write_info (png_ptr, png_info);
	png_write_image (png_ptr, image);
	png_write_end (png_ptr, png_info);
	png_destroy_write_struct (&png_ptr, &png_info);

	return 0;
}