[libpng16] Made makepng and pngtest produce identical PNGs, add "--relaxed"

option to pngtest. The "--relaxed" option turns off the benign errors that are
enabled by default in pre-RC builds. makepng can now write ICC profiles
where the length has not been extended to a multiple of 4, and pngtest
now intercepts all libpng errors, allowing the previously-introduced
"--strict test" on no warnings to actually work.

ANNOUNCE

@@ -488,6 +488,12 @@ Version 1.6.0beta29 [September 1, 2012]
   Added contrib/examples/* to the *.zip and *.7z distributions.
   Updated simplified API synopses and description of the png_image structure
     in the manual.
+  Made makepng and pngtest produce identical PNGs, add "--relaxed" option
+    to pngtest. The "--relaxed" option turns off the benign errors that are
+    enabled by default in pre-RC builds. makepng can now write ICC profiles
+    where the length has not been extended to a multiple of 4, and pngtest
+    now intercepts all libpng errors, allowing the previously-introduced
+    "--strict test" on no warnings to actually work.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

CHANGES

@@ -4240,6 +4240,12 @@ Version 1.6.0beta29 [September 1, 2012]
   Added contrib/examples/* to the *.zip and *.7z distributions.
   Updated simplified API synopses and description of the png_image structure
     in the manual.
+  Made makepng and pngtest produce identical PNGs, add "--relaxed" option
+    to pngtest. The "--relaxed" option turns off the benign errors that are
+    enabled by default in pre-RC builds. makepng can now write ICC profiles
+    where the length has not been extended to a multiple of 4, and pngtest
+    now intercepts all libpng errors, allowing the previously-introduced
+    "--strict test" on no warnings to actually work.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

contrib/libtests/makepng.c

@@ -392,11 +392,36 @@ generate_row(png_bytep row, size_t rowbytes, unsigned int y, int color_type,
    }
 }
 
-static int /* 0 on success, else an error code */
+
-write_png(FILE *fp, int color_type, int bit_depth,
+static void PNGCBAPI
-   volatile png_fixed_point gamma, chunk_insert * volatile insert)
+makepng_warning(png_structp png_ptr, png_const_charp message)
 {
-   png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,0,0,0);
+   const char **ep = png_get_error_ptr(png_ptr);
+   const char *name;
+
+   if (ep != NULL && *ep != NULL)
+      name = *ep;
+
+   else
+      name = "makepng";
+
+  fprintf(stderr, "%s: warning: %s\n", name, message);
+}
+
+static void PNGCBAPI
+makepng_error(png_structp png_ptr, png_const_charp message)
+{
+   makepng_warning(png_ptr, message);
+   png_longjmp(png_ptr, 1);
+}
+
+static int /* 0 on success, else an error code */
+write_png(const char **name, FILE *fp, int color_type, int bit_depth,
+   volatile png_fixed_point gamma, chunk_insert * volatile insert,
+   unsigned int filters)
+{
+   png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
+      name, makepng_error, makepng_warning);
    volatile png_infop info_ptr = NULL;
    volatile png_bytep row = NULL;
 
@@ -517,7 +542,7 @@ write_png(FILE *fp, int color_type, int bit_depth,
       png_write_info(png_ptr, info_ptr);
 
       /* Restrict the filters */
-      png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, PNG_NO_FILTERS);
+      png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, filters);
 
       {
          int passes = png_set_interlace_handling(png_ptr);
@@ -604,7 +629,10 @@ load_file(png_const_charp name, png_bytepp result)
 
                if (total > 0)
                {
-                  png_bytep data = malloc(total);
+                  /* Round up to a multiple of 4 here to allow an iCCP profile
+                   * to be padded to a 4x boundary.
+                   */
+                  png_bytep data = malloc((total+3)&~3);
 
                   if (data != NULL)
                   {
@@ -729,12 +757,13 @@ insert_iCCP(png_structp png_ptr, png_infop info_ptr, int nparams,
       case '<':
          {
             png_size_t filelen = load_file(params[1]+1, &profile);
-            if (filelen > 0xffffffff) /* Maximum profile length */
+            if (filelen > 0xfffffffc) /* Maximum profile length */
             {
                fprintf(stderr, "%s: file too long (%lu) for an ICC profile\n",
                   params[1]+1, (unsigned long)filelen);
                exit(1);
             }
+
             proflen = (png_uint_32)filelen;
          }
          break;
@@ -771,9 +800,14 @@ insert_iCCP(png_structp png_ptr, png_infop info_ptr, int nparams,
    if (proflen & 3)
    {
       fprintf(stderr,
-         "--insert iCCP %s: profile length must be a multiple of 4\n",
+         "makepng: --insert iCCP %s: profile length made a multiple of 4\n",
          params[1]);
-      result = 0; /* Cannot fix this! */
+
+      /* load_file allocates extra space for this padding, the ICC spec requires
+       * padding with zero bytes.
+       */
+      while (proflen & 3)
+         profile[proflen++] = 0;
    }
 
    if (profile != NULL && proflen > 3)
@@ -1067,6 +1101,7 @@ main(int argc, char **argv)
    const char *file_name = NULL;
    int color_type = 8; /* invalid */
    int bit_depth = 32; /* invalid */
+   unsigned int filters = PNG_ALL_FILTERS;
    png_fixed_point gamma = 0; /* not set */
    chunk_insert *head_insert = NULL;
    chunk_insert **insert_ptr = &head_insert;
@@ -1093,6 +1128,12 @@ main(int argc, char **argv)
          continue;
       }
 
+      if (strcmp(arg, "--nofilters") == 0)
+      {
+         filters = PNG_FILTER_NONE;
+         continue;
+      }
+
       if (argc >= 3 && strcmp(arg, "--insert") == 0)
       {
          png_const_charp what = *++argv;
@@ -1209,8 +1250,30 @@ main(int argc, char **argv)
       exit(1);
    }
 
+   /* Restrict the filters for more speed to those we know are used for the
+    * generated images.
+    */
+   if (filters == PNG_ALL_FILTERS)
    {
-      int ret = write_png(fp, color_type, bit_depth, gamma, head_insert);
+      if ((color_type & PNG_COLOR_MASK_PALETTE) != 0 || bit_depth < 8)
+         filters = PNG_FILTER_NONE;
+
+      else if (color_type & PNG_COLOR_MASK_COLOR) /* rgb */
+      {
+         if (bit_depth == 8)
+            filters &= ~(PNG_FILTER_NONE | PNG_FILTER_AVG);
+
+         else
+            filters = PNG_FILTER_SUB | PNG_FILTER_PAETH;
+      }
+
+      else /* gray 8 or 16-bit */
+         filters &= ~PNG_FILTER_NONE;
+   }
+
+   {
+      int ret = write_png(&file_name, fp, color_type, bit_depth, gamma,
+         head_insert, filters);
 
       if (ret != 0 && file_name != NULL)
          remove(file_name);

pngtest.c

@@ -95,6 +95,7 @@ static char tIME_string[PNG_tIME_STRING_LENGTH] = "tIME chunk is not present";
 
 static int verbose = 0;
 static int strict = 0;
+static int relaxed = 0;
 static int unsupported_chunks = 0; /* chunk unsupported by libpng in input */
 static int error_count = 0; /* count calls to png_error */
 static int warning_count = 0; /* count calls to png_warning */
@@ -395,6 +396,7 @@ pngtest_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
    pngtest_check_io_state(png_ptr, length, PNG_IO_WRITING);
 #endif
 }
+#endif /* !PNG_STDIO_SUPPORTED */
 
 /* This function is called when there is a warning, but the library thinks
  * it can continue anyway.  Replacement functions don't have to do anything
@@ -405,16 +407,15 @@ static void PNGCBAPI
 pngtest_warning(png_structp png_ptr, png_const_charp message)
 {
    PNG_CONST char *name = "UNKNOWN (ERROR!)";
-   char *test;
+   PNG_CONST char **test= (PNG_CONST char **)png_get_error_ptr(png_ptr);
-   test = png_get_error_ptr(png_ptr);
 
    ++warning_count;
 
-   if (test == NULL)
+   if (test == NULL || *test == NULL)
      fprintf(STDERR, "%s: libpng warning: %s\n", name, message);
 
    else
-     fprintf(STDERR, "%s: libpng warning: %s\n", test, message);
+     fprintf(STDERR, "%s: libpng warning: %s\n", *test, message);
 }
 
 /* This is the default error handling function.  Note that replacements for
@@ -432,7 +433,7 @@ pngtest_error(png_structp png_ptr, png_const_charp message)
     * actually OK in this case.
     */
 }
-#endif /* !PNG_STDIO_SUPPORTED */
+
 /* END of code to validate stdio-free compilation */
 
 /* START of code to validate memory allocation and deallocation */
@@ -799,6 +800,7 @@ test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
 {
    static png_FILE_p fpin;
    static png_FILE_p fpout;  /* "static" prevents setjmp corruption */
+   static PNG_CONST char *fp_name;
    png_structp read_ptr;
    png_infop read_info_ptr, end_info_ptr;
 #ifdef PNG_WRITE_SUPPORTED
@@ -817,6 +819,7 @@ test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
    int bit_depth, color_type;
 
    row_buf = NULL;
+   fp_name = inname;
 
    if ((fpin = fopen(inname, "rb")) == NULL)
    {
@@ -840,10 +843,7 @@ test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
    read_ptr =
       png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
 #endif
-#ifndef PNG_STDIO_SUPPORTED
+   png_set_error_fn(read_ptr, &fp_name, pngtest_error, pngtest_warning);
-   png_set_error_fn(read_ptr, (png_voidp)inname, pngtest_error,
-       pngtest_warning);
-#endif
 
 #ifdef PNG_WRITE_SUPPORTED
 #if defined(PNG_USER_MEM_SUPPORTED) && PNG_DEBUG
@@ -854,10 +854,7 @@ test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
    write_ptr =
       png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
 #endif
-#ifndef PNG_STDIO_SUPPORTED
+   png_set_error_fn(write_ptr, &fp_name, pngtest_error, pngtest_warning);
-   png_set_error_fn(write_ptr, (png_voidp)inname, pngtest_error,
-       pngtest_warning);
-#endif
 #endif
    pngtest_debug("Allocating read_info, write_info and end_info structures");
    read_info_ptr = png_create_info_struct(read_ptr);
@@ -918,7 +915,20 @@ test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
       png_set_benign_errors(write_ptr, 0);
 #endif
 
-      /* if strict is not set, then both are treated as warnings. */
+      /* if strict is not set, then app warnings and errors are treated as
+       * warnings in release builds, but not in unstable builds; this can be
+       * changed with '--relaxed'.
+       */
+   }
+   
+   else if (relaxed)
+   {
+      /* Allow application (pngtest) errors and warnings to pass */
+      png_set_benign_errors(read_ptr, 1);
+
+#ifdef PNG_WRITE_SUPPORTED
+      png_set_benign_errors(write_ptr, 1);
+#endif
    }
 
    pngtest_debug("Initializing input and output streams");
@@ -939,14 +949,6 @@ test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
 #  endif
 #endif
 
-#ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
-   /* Normally one would use Z_DEFAULT_STRATEGY for text compression.
-    * This is here just to make pngtest replicate the results from libpng
-    * versions prior to 1.5.4, and to test this new API.
-    */
-   png_set_text_compression_strategy(write_ptr, Z_FILTERED);
-#endif
-
    if (status_dots_requested == 1)
    {
 #ifdef PNG_WRITE_SUPPORTED
@@ -1451,6 +1453,14 @@ test_one_file(PNG_CONST char *inname, PNG_CONST char *outname)
 #endif
 
 #ifdef PNG_WRITE_SUPPORTED
+#ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
+   /* Normally one would use Z_DEFAULT_STRATEGY for text compression.
+    * This is here just to make pngtest replicate the results from libpng
+    * versions prior to 1.5.4, and to test this new API.
+    */
+   png_set_text_compression_strategy(write_ptr, Z_FILTERED);
+#endif
+
    /* When the unknown vpAg/sTER chunks are written by pngtest the only way to
     * do it is to write them *before* calling png_write_end.  When unknown
     * chunks are written by libpng, however, they are written just before IEND.     * There seems to be no way round this, however vpAg/sTER are not expected
@@ -1703,6 +1713,16 @@ main(int argc, char *argv[])
          verbose = 1;
          inname = argv[2];
          strict++;
+         relaxed = 0;
+      }
+
+      else if (strcmp(argv[1], "--relaxed") == 0)
+      {
+         status_dots_requested = 0;
+         verbose = 1;
+         inname = argv[2];
+         strict = 0;
+         relaxed++;
       }
 
       else