diff --git a/contrib/pngminus/pnm2png.c b/contrib/pngminus/pnm2png.c
index e720085..3d4c6c5 100644
--- a/contrib/pngminus/pnm2png.c
+++ b/contrib/pngminus/pnm2png.c
@@ -1,14 +1,15 @@
 /*
  *  pnm2png.c --- conversion from PBM/PGM/PPM-file to PNG-file
- *  copyright (C) 1999,2015,2017 by Willem van Schaik <willem at schaik.com>
+ *  copyright (C) 1999,2015,2017,2018 by Willem van Schaik <willem at schaik.com>
  *
  *  version 1.0 - 1999.10.15 - First version.
- *  version 1.1 - 2015.07.29 - Fixed leaks (Glenn Randers-Pehrson)
- *  version 1.2 - 2017.04.22 - Add buffer-size check
+ *          1.1 - 2015.07.29 - Fixed leaks (Glenn Randers-Pehrson)
+ *          1.2 - 2017.04.22 - Add buffer-size check
  *          1.3 - 2017.08.24 - Fix potential overflow in buffer-size check
  *                             (Glenn Randers-Pehrson)
  *          1.4 - 2017.08.28 - Add PNGMINUS_UNUSED (Christian Hesse)
  *          1.5 - 2018.08.05 - Fix buffer overflow in tokenizer (Cosmin Truta)
+ *          1.6 - 2018.08.05 - Improve portability and fix style (Cosmin Truta)
  *
  *  Permission to use, copy, modify, and distribute this software and
  *  its documentation for any purpose and without fee is hereby granted,
@@ -20,11 +21,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
-#ifdef __TURBOC__
-#include <mem.h>
 #include <fcntl.h>
-#endif
-#include <zlib.h>
 
 #ifndef BOOL
 #define BOOL unsigned char
@@ -36,38 +33,20 @@
 #define FALSE (BOOL) 0
 #endif
 
-#define STDIN  0
-#define STDOUT 1
-#define STDERR 2
-
-/* to make pnm2png verbose so we can find problems (needs to be before png.h) */
+/* make pnm2png verbose so we can find problems (needs to be before png.h) */
 #ifndef PNG_DEBUG
 #define PNG_DEBUG 0
 #endif
 
 #include "png.h"
 
-/* Define png_jmpbuf() in case we are using a pre-1.0.6 version of libpng */
-#ifndef png_jmpbuf
-#  define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf)
-#endif
-
-#ifndef PNGMINUS_UNUSED
-/* Unused formal parameter warnings are silenced using the following macro
- * which is expected to have no bad effects on performance (optimizing
- * compilers will probably remove it entirely).
- */
-#  define PNGMINUS_UNUSED(param) (void)param
-#endif
-
-
 /* function prototypes */
 
-int  main (int argc, char *argv[]);
+int main (int argc, char *argv[]);
 void usage ();
-BOOL pnm2png (FILE *pnm_file, FILE *png_file, FILE *alpha_file, BOOL interlace,
-    BOOL alpha);
-void get_token(FILE *pnm_file, char *token_buf, size_t token_buf_size);
+BOOL pnm2png (FILE *pnm_file, FILE *png_file, FILE *alpha_file,
+              BOOL interlace, BOOL alpha);
+void get_token (FILE *pnm_file, char *token_buf, size_t token_buf_size);
 png_uint_32 get_data (FILE *pnm_file, int depth);
 png_uint_32 get_value (FILE *pnm_file, int depth);
 
@@ -75,7 +54,7 @@
  *  main
  */
 
-int main(int argc, char *argv[])
+int main (int argc, char *argv[])
 {
   FILE *fp_rd = stdin;
   FILE *fp_al = NULL;
@@ -100,20 +79,20 @@
           {
             fprintf (stderr, "PNM2PNG\n");
             fprintf (stderr, "Error:  alpha-channel file %s does not exist\n",
-               argv[argi]);
+                     argv[argi]);
             exit (1);
           }
           break;
         case 'h':
         case '?':
-          usage();
-          exit(0);
+          usage ();
+          exit (0);
           break;
         default:
           fprintf (stderr, "PNM2PNG\n");
           fprintf (stderr, "Error:  unknown option %s\n", argv[argi]);
-          usage();
-          exit(1);
+          usage ();
+          exit (1);
           break;
       } /* end switch */
     }
@@ -131,7 +110,7 @@
       if ((fp_wr = fopen (argv[argi], "wb")) == NULL)
       {
         fprintf (stderr, "PNM2PNG\n");
-        fprintf (stderr, "Error:  can not create PNG-file %s\n", argv[argi]);
+        fprintf (stderr, "Error:  cannot create PNG-file %s\n", argv[argi]);
         exit (1);
       }
     }
@@ -139,21 +118,19 @@
     {
       fprintf (stderr, "PNM2PNG\n");
       fprintf (stderr, "Error:  too many parameters\n");
-      usage();
+      usage ();
       exit (1);
     }
   } /* end for */
 
-#ifdef __TURBOC__
-  /* set stdin/stdout to binary, we're reading the PNM always! in binary format */
+#if defined(O_BINARY) && (O_BINARY != 0)
+  /* set stdin/stdout to binary,
+   * we're reading the PNM always! in binary format
+   */
   if (fp_rd == stdin)
-  {
-    setmode (STDIN, O_BINARY);
-  }
+    setmode (fileno (stdin), O_BINARY);
   if (fp_wr == stdout)
-  {
-    setmode (STDOUT, O_BINARY);
-  }
+    setmode (fileno (stdout), O_BINARY);
 #endif
 
   /* call the conversion program itself */
@@ -179,15 +156,10 @@
  *  usage
  */
 
-void usage()
+void usage ()
 {
   fprintf (stderr, "PNM2PNG\n");
   fprintf (stderr, "   by Willem van Schaik, 1999\n");
-#ifdef __TURBOC__
-  fprintf (stderr, "   for Turbo-C and Borland-C compilers\n");
-#else
-  fprintf (stderr, "   for Linux (and Unix) compilers\n");
-#endif
   fprintf (stderr, "Usage:  pnm2png [options] <file>.<pnm> [<file>.png]\n");
   fprintf (stderr, "   or:  ... | pnm2png [options]\n");
   fprintf (stderr, "Options:\n");
@@ -201,31 +173,31 @@
  *  pnm2png
  */
 
-BOOL pnm2png (FILE *pnm_file, FILE *png_file, FILE *alpha_file, BOOL interlace,
-     BOOL alpha)
+BOOL pnm2png (FILE *pnm_file, FILE *png_file, FILE *alpha_file,
+              BOOL interlace, BOOL alpha)
 {
   png_struct    *png_ptr = NULL;
   png_info      *info_ptr = NULL;
   png_byte      *png_pixels = NULL;
   png_byte      **row_pointers = NULL;
   png_byte      *pix_ptr = NULL;
-  volatile png_uint_32   row_bytes;
+  volatile png_uint_32 row_bytes;
 
   char          type_token[16];
   char          width_token[16];
   char          height_token[16];
   char          maxval_token[16];
-  volatile int    color_type=1;
-  unsigned long   ul_width=0, ul_alpha_width=0;
-  unsigned long   ul_height=0, ul_alpha_height=0;
-  unsigned long   ul_maxval=0;
-  volatile png_uint_32   width=0, height=0;
-  volatile png_uint_32   alpha_width=0, alpha_height=0;
+  volatile int  color_type = 1;
+  unsigned long ul_width = 0, ul_alpha_width = 0;
+  unsigned long ul_height = 0, ul_alpha_height = 0;
+  unsigned long ul_maxval = 0;
+  volatile png_uint_32 width = 0, height = 0;
+  volatile png_uint_32 alpha_width = 0, alpha_height = 0;
   png_uint_32   maxval;
-  volatile int           bit_depth = 0;
-  int           channels=0;
+  volatile int  bit_depth = 0;
+  int           channels = 0;
   int           alpha_depth = 0;
-  int           alpha_present=0;
+  int           alpha_present = 0;
   int           row, col;
   BOOL          raw, alpha_raw = FALSE;
 #if defined(PNG_WRITE_INVERT_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
@@ -236,7 +208,7 @@
 
   /* read header of PNM file */
 
-  get_token(pnm_file, type_token, sizeof (type_token));
+  get_token (pnm_file, type_token, sizeof (type_token));
   if (type_token[0] != 'P')
   {
     return FALSE;
@@ -246,30 +218,31 @@
 #if defined(PNG_WRITE_INVERT_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
     raw = (type_token[1] == '4');
     color_type = PNG_COLOR_TYPE_GRAY;
-    get_token(pnm_file, width_token, sizeof (width_token));
+    get_token (pnm_file, width_token, sizeof (width_token));
     sscanf (width_token, "%lu", &ul_width);
     width = (png_uint_32) ul_width;
-    get_token(pnm_file, height_token, sizeof (height_token));
+    get_token (pnm_file, height_token, sizeof (height_token));
     sscanf (height_token, "%lu", &ul_height);
     height = (png_uint_32) ul_height;
     bit_depth = 1;
     packed_bitmap = TRUE;
 #else
-    fprintf (stderr, "PNM2PNG built without PNG_WRITE_INVERT_SUPPORTED and \n");
+    fprintf (stderr, "PNM2PNG built without PNG_WRITE_INVERT_SUPPORTED and\n");
     fprintf (stderr, "PNG_WRITE_PACK_SUPPORTED can't read PBM (P1,P4) files\n");
+    return FALSE;
 #endif
   }
   else if ((type_token[1] == '2') || (type_token[1] == '5'))
   {
     raw = (type_token[1] == '5');
     color_type = PNG_COLOR_TYPE_GRAY;
-    get_token(pnm_file, width_token, sizeof (width_token));
+    get_token (pnm_file, width_token, sizeof (width_token));
     sscanf (width_token, "%lu", &ul_width);
     width = (png_uint_32) ul_width;
-    get_token(pnm_file, height_token, sizeof (height_token));
+    get_token (pnm_file, height_token, sizeof (height_token));
     sscanf (height_token, "%lu", &ul_height);
     height = (png_uint_32) ul_height;
-    get_token(pnm_file, maxval_token, sizeof (maxval_token));
+    get_token (pnm_file, maxval_token, sizeof (maxval_token));
     sscanf (maxval_token, "%lu", &ul_maxval);
     maxval = (png_uint_32) ul_maxval;
 
@@ -281,20 +254,22 @@
       bit_depth = 4;
     else if (maxval <= 255)
       bit_depth = 8;
-    else /* if (maxval <= 65535) */
+    else if (maxval <= 65535U)
       bit_depth = 16;
+    else /* maxval > 65535U */
+      return FALSE;
   }
   else if ((type_token[1] == '3') || (type_token[1] == '6'))
   {
     raw = (type_token[1] == '6');
     color_type = PNG_COLOR_TYPE_RGB;
-    get_token(pnm_file, width_token, sizeof (width_token));
+    get_token (pnm_file, width_token, sizeof (width_token));
     sscanf (width_token, "%lu", &ul_width);
     width = (png_uint_32) ul_width;
-    get_token(pnm_file, height_token, sizeof (height_token));
+    get_token (pnm_file, height_token, sizeof (height_token));
     sscanf (height_token, "%lu", &ul_height);
     height = (png_uint_32) ul_height;
-    get_token(pnm_file, maxval_token, sizeof (maxval_token));
+    get_token (pnm_file, maxval_token, sizeof (maxval_token));
     sscanf (maxval_token, "%lu", &ul_maxval);
     maxval = (png_uint_32) ul_maxval;
     if (maxval <= 1)
@@ -305,8 +280,10 @@
       bit_depth = 4;
     else if (maxval <= 255)
       bit_depth = 8;
-    else /* if (maxval <= 65535) */
+    else if (maxval <= 65535U)
       bit_depth = 16;
+    else /* maxval > 65535U */
+      return FALSE;
   }
   else
   {
@@ -322,7 +299,7 @@
     if (color_type == PNG_COLOR_TYPE_RGB)
       color_type = PNG_COLOR_TYPE_RGB_ALPHA;
 
-    get_token(alpha_file, type_token, sizeof (type_token));
+    get_token (alpha_file, type_token, sizeof (type_token));
     if (type_token[0] != 'P')
     {
       return FALSE;
@@ -330,17 +307,17 @@
     else if ((type_token[1] == '2') || (type_token[1] == '5'))
     {
       alpha_raw = (type_token[1] == '5');
-      get_token(alpha_file, width_token, sizeof (width_token));
+      get_token (alpha_file, width_token, sizeof (width_token));
       sscanf (width_token, "%lu", &ul_alpha_width);
-      alpha_width=(png_uint_32) ul_alpha_width;
+      alpha_width = (png_uint_32) ul_alpha_width;
       if (alpha_width != width)
         return FALSE;
-      get_token(alpha_file, height_token, sizeof (height_token));
+      get_token (alpha_file, height_token, sizeof (height_token));
       sscanf (height_token, "%lu", &ul_alpha_height);
       alpha_height = (png_uint_32) ul_alpha_height;
       if (alpha_height != height)
         return FALSE;
-      get_token(alpha_file, maxval_token, sizeof (maxval_token));
+      get_token (alpha_file, maxval_token, sizeof (maxval_token));
       sscanf (maxval_token, "%lu", &ul_maxval);
       maxval = (png_uint_32) ul_maxval;
       if (maxval <= 1)
@@ -351,8 +328,10 @@
         alpha_depth = 4;
       else if (maxval <= 255)
         alpha_depth = 8;
-      else /* if (maxval <= 65535) */
+      else if (maxval <= 65535U)
         alpha_depth = 16;
+      else /* maxval > 65535U */
+        return FALSE;
       if (alpha_depth != bit_depth)
         return FALSE;
     }
@@ -380,21 +359,29 @@
 
 #if defined(PNG_WRITE_INVERT_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
   if (packed_bitmap)
+  {
     /* row data is as many bytes as can fit width x channels x bit_depth */
     row_bytes = (width * channels * bit_depth + 7) / 8;
+  }
   else
 #endif
-  /* row_bytes is the width x number of channels x (bit-depth / 8) */
-    row_bytes = width * channels * ((bit_depth <= 8) ? 1 : 2);
-
-  if ((row_bytes == 0 || (size_t)height > ((size_t)(-1))/(size_t)row_bytes))
   {
-    /* too big */ 
+    /* row_bytes is the width x number of channels x (bit-depth / 8) */
+    row_bytes = width * channels * ((bit_depth <= 8) ? 1 : 2);
+  }
+
+  if ((row_bytes == 0) ||
+      ((size_t) height > (size_t) (-1) / (size_t) row_bytes))
+  {
+    /* too big */
     return FALSE;
   }
   if ((png_pixels = (png_byte *)
-     malloc ((size_t)row_bytes * (size_t)height * sizeof (png_byte))) == NULL)
+       malloc ((size_t) row_bytes * (size_t) height)) == NULL)
+  {
+    /* out of memory */
     return FALSE;
+  }
 
   /* read data from PNM file */
   pix_ptr = png_pixels;
@@ -405,9 +392,12 @@
     if (packed_bitmap)
     {
       for (i = 0; i < (int) row_bytes; i++)
+      {
         /* png supports this format natively so no conversion is needed */
         *pix_ptr++ = get_data (pnm_file, 8);
-    } else
+      }
+    }
+    else
 #endif
     {
       for (col = 0; col < (int) width; col++)
@@ -415,10 +405,15 @@
         for (i = 0; i < (channels - alpha_present); i++)
         {
           if (raw)
+          {
             *pix_ptr++ = get_data (pnm_file, bit_depth);
+          }
           else
+          {
             if (bit_depth <= 8)
+            {
               *pix_ptr++ = get_value (pnm_file, bit_depth);
+            }
             else
             {
               tmp16 = get_value (pnm_file, bit_depth);
@@ -427,41 +422,46 @@
               *pix_ptr = (png_byte) (tmp16 & 0xFF);
               pix_ptr++;
             }
+          }
         }
 
         if (alpha) /* read alpha-channel from pgm file */
         {
           if (alpha_raw)
+          {
             *pix_ptr++ = get_data (alpha_file, alpha_depth);
+          }
           else
+          {
             if (alpha_depth <= 8)
+            {
               *pix_ptr++ = get_value (alpha_file, bit_depth);
+            }
             else
             {
               tmp16 = get_value (alpha_file, bit_depth);
               *pix_ptr++ = (png_byte) ((tmp16 >> 8) & 0xFF);
               *pix_ptr++ = (png_byte) (tmp16 & 0xFF);
             }
-        } /* if alpha */
-      } /* if packed_bitmap */
+          }
+        } /* end if alpha */
+      } /* end if packed_bitmap */
     } /* end for col */
   } /* end for row */
 
   /* prepare the standard PNG structures */
-  png_ptr = png_create_write_struct (png_get_libpng_ver(NULL), NULL, NULL,
-      NULL);
+  png_ptr = png_create_write_struct (png_get_libpng_ver(NULL),
+                                     NULL, NULL, NULL);
   if (!png_ptr)
   {
     free (png_pixels);
-    png_pixels = NULL;
     return FALSE;
   }
   info_ptr = png_create_info_struct (png_ptr);
   if (!info_ptr)
   {
-    png_destroy_write_struct (&png_ptr, (png_infopp) NULL);
+    png_destroy_write_struct (&png_ptr, NULL);
     free (png_pixels);
-    png_pixels = NULL;
     return FALSE;
   }
 
@@ -473,12 +473,10 @@
   }
 #endif
 
-  /* setjmp() must be called in every function that calls a PNG-reading libpng function */
-  if (setjmp (png_jmpbuf(png_ptr)))
+  if (setjmp (png_jmpbuf (png_ptr)))
   {
     png_destroy_write_struct (&png_ptr, &info_ptr);
     free (png_pixels);
-    png_pixels = NULL;
     return FALSE;
   }
 
@@ -487,21 +485,20 @@
 
   /* we're going to write more or less the same PNG as the input file */
   png_set_IHDR (png_ptr, info_ptr, width, height, bit_depth, color_type,
-    (!interlace) ? PNG_INTERLACE_NONE : PNG_INTERLACE_ADAM7,
-    PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+                (!interlace) ? PNG_INTERLACE_NONE : PNG_INTERLACE_ADAM7,
+                PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
 
   /* write the file header information */
   png_write_info (png_ptr, info_ptr);
 
   /* if needed we will allocate memory for an new array of row-pointers */
-  if (row_pointers == (unsigned char**) NULL)
+  if (row_pointers == NULL)
   {
     if ((row_pointers = (png_byte **)
-        malloc (height * sizeof (png_bytep))) == NULL)
+         malloc (height * sizeof (png_byte *))) == NULL)
     {
       png_destroy_write_struct (&png_ptr, &info_ptr);
       free (png_pixels);
-      png_pixels = NULL;
       return FALSE;
     }
   }
@@ -519,21 +516,19 @@
   /* clean up after the write, and free any memory allocated */
   png_destroy_write_struct (&png_ptr, &info_ptr);
 
-  if (row_pointers != (unsigned char**) NULL)
+  if (row_pointers != NULL)
     free (row_pointers);
-  if (png_pixels != (unsigned char*) NULL)
+  if (png_pixels != NULL)
     free (png_pixels);
 
-  PNGMINUS_UNUSED(raw); /* Quiet a Coverity defect */
-
   return TRUE;
 } /* end of pnm2png */
 
 /*
- * get_token() - gets the first string after whitespace
+ * get_token - gets the first string after whitespace
  */
 
-void get_token(FILE *pnm_file, char *token_buf, size_t token_buf_size)
+void get_token (FILE *pnm_file, char *token_buf, size_t token_buf_size)
 {
   size_t i = 0;
   int ret;
@@ -541,13 +536,13 @@
   /* remove white-space and comment lines */
   do
   {
-    ret = fgetc(pnm_file);
+    ret = fgetc (pnm_file);
     if (ret == '#')
     {
       /* the rest of this line is a comment */
       do
       {
-        ret = fgetc(pnm_file);
+        ret = fgetc (pnm_file);
       }
       while ((ret != '\n') && (ret != '\r') && (ret != EOF));
     }
@@ -559,7 +554,7 @@
   /* read string */
   do
   {
-    ret = fgetc(pnm_file);
+    ret = fgetc (pnm_file);
     if (ret == EOF) break;
     if (++i == token_buf_size - 1) break;
     token_buf[i] = (char) ret;
@@ -572,9 +567,9 @@
 }
 
 /*
- * get_data() - takes first byte and converts into next pixel value,
- *        taking as much bits as defined by bit-depth and
- *        using the bit-depth to fill up a byte (0Ah -> AAh)
+ *  get_data - takes first byte and converts into next pixel value,
+ *             taking as much bits as defined by bit-depth and
+ *             using the bit-depth to fill up a byte (0Ah -> AAh)
  */
 
 png_uint_32 get_data (FILE *pnm_file, int depth)
@@ -606,8 +601,8 @@
 }
 
 /*
- * get_value() - takes first (numeric) string and converts into number,
- *         using the bit-depth to fill up a byte (0Ah -> AAh)
+ *  get_value - takes first (numeric) string and converts into number,
+ *              using the bit-depth to fill up a byte (0Ah -> AAh)
  */
 
 png_uint_32 get_value (FILE *pnm_file, int depth)
@@ -636,4 +631,3 @@
 }
 
 /* end of source */
-