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

typedef int _;
typedef double f;

png_image I;
png_bytep D[2];
_ A,N,G,E, *l, *d, s, i, j,
  c[82],
  t;

f x, y, X, Y, U, V,
  v[3][2],
  b[3][6],
  e[6561][6],
  Z[6] = {1, 0, 0,  0, 1, 0};

_ k(_ a, char *r)
{
   return printf(a ? a - 1 ? "Error writing %s\n"
                           : "Error reading %s\n"
                   : "%s <input.png> <output1.png> <output2.png>\n",
                 r);
}

f R(f r)
{
   return (f)rand() / (RAND_MAX + 1u) * r;
}

void T(_ h, f *p)
{
   f *a, q[6];
   _ r;

   if( h > 7 )
      memcpy(e[t++], p, 6 * sizeof(f));
   else
      for(r = 0; r < 3; T(h + 1, q))
      {
         a = b[r++];
         q[0] = a[0] * p[0] + a[1] * p[3];
         q[1] = a[0] * p[1] + a[1] * p[4];
         q[2] = a[0] * p[2] + a[1] * p[5] + a[2];

         q[3] = a[3] * p[0] + a[4] * p[3];
         q[4] = a[3] * p[1] + a[4] * p[4];
         q[5] = a[3] * p[2] + a[4] * p[5] + a[5];
      }
}

f P(f m, f n, f p, f q, f g, f h)
{
   return fabs((p - m) * (h - n) - (q - n) * (g - m));
}

_ main(_ a, char **r)
{
   if( a - 4 )
      return k(0, *r);

   I.version = PNG_IMAGE_VERSION;
   if( png_image_begin_read_from_file(&I, r[1]) )
   {
      G = I.width;
      E = I.height;
      for(I.format = PNG_FORMAT_RGBA; i < 2;)
         D[i++] = (png_bytep)calloc(s = G * E, 4);
      A = *D &&
          D[1] &&
          png_image_finish_read(&I, NULL, *D, 0, NULL);
   }
   if( !A )
      return k(1, r[1]);

   srand(time(NULL));

   for(U = 0;
       U < 0.4;
       U = P(v[0][0], v[0][1], v[1][0], v[1][1], v[2][0], v[2][1]))
      for(i = 0; i < 3; i++)
         for(j = 0; j < 2;)
            v[i][j++] = R(0.8) + 0.1;

   for(i = 0; i < 3; i++)
   {
      if( sizeof('c') > 1 )
      {
         b[i][0] = x = R(0.6) + 0.1 * (i + 2);
         b[i][4] = y = R(0.6) + 0.1 * (i + 2);
         b[i][1] = b[i][3] = 0.0;
         b[i][2] = v[i][0] - x * 0.5;
         b[i][5] = v[i][1] - y * 0.5;
      }
      else
      {
         for(U = 0;
             U < 0.3 || U > 0.7;
             U = P(b[i][0], b[i][1], b[i][2], b[i][3], b[i][4], b[i][5]))
            for(j = 0; j < 6; j++)
               b[i][j] = v[i][j % 2] + R(1) - 0.5;

         X = b[i][2];
         Y = b[i][3];
         U = b[i][4];
         V = b[i][5];

         b[i][2] = x = b[i][0];
         b[i][5] = y = b[i][1];

         b[i][0] = X - x;
         b[i][3] = Y - y;

         b[i][1] = U - x;
         b[i][4] = V - y;
      }
   }

   T(0, Z);

   for(d = (_*)D[1]; N < s * 80;
       N +=
          i < 0 || j < 0 || i >= G || j >= E
          ? 1
          : d[j * G + i]++ > 79 ? s * 80 : 0)
   {
      x = R(1);
      y = R(1);
      for(i = 0; i < 2; i++)
      {
         A = R(6561);
         X = x * e[A][0] + y * e[A][1] + e[A][2];
         Y = x * e[A][3] + y * e[A][4] + e[A][5];
         x = X;
         y = Y;
      }

      i = round(x * G);
      j = round(y * E);
   }

   for(i = j = 0; i < s;)
      c[d[i++]]++;
   for(A = 80; A > 1 && (j += c[A]) < s / 2; A--);

   l = (_*)*D;
   for(i = 0; i++ < s; d++, *l++ *= j)
      *d = (j = *d < A) ? 0 : *l;

   for(i = 0; i < 2; i++)
      if( !png_image_write_to_file(&I, r[i + 2], 0, D[i], 0, NULL) )
         return k(2, r[i + 2]);

   return 0;
}