Committing in .

[wxWidgets.git] / src / png / libpng.txt

diff --git a/src/png/libpng.txt b/src/png/libpng.txt
index 07fc3cd2878898070f3665023f5de9a53c2a6d9f..0324715bb29293ef2c3e7246a690428d56f0252a 100644 (file)
--- a/src/png/libpng.txt
+++ b/src/png/libpng.txt
@@ -1,9 +1,9 @@
 libpng.txt - A description on how to use and modify libpng
 
 libpng.txt - A description on how to use and modify libpng
 

- libpng version 1.2.5rc3 - September 18, 2002
+ libpng version 1.2.6 - August 15, 2004

  Updated and distributed by Glenn Randers-Pehrson
  Updated and distributed by Glenn Randers-Pehrson

- <randeg@alum.rpi.edu>
- Copyright (c) 1998-2002 Glenn Randers-Pehrson
+ <glennrp@users.sourceforge.net>
+ Copyright (c) 1998-2004 Glenn Randers-Pehrson

  For conditions of distribution and use, see copyright
  notice in png.h.
 
  For conditions of distribution and use, see copyright
  notice in png.h.
 


@@ -300,6 +300,28 @@ To inform libpng about your function, use
 
     png_set_read_status_fn(png_ptr, read_row_callback);
 
 
     png_set_read_status_fn(png_ptr, read_row_callback);
 

+Width and height limits
+
+The PNG specification allows the width and height of an image to be as
+large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns.
+Since very few applications really need to process such large images,
+we have imposed an arbitrary 1-million limit on rows and columns.
+Larger images will be rejected immediately with a png_error() call. If
+you wish to override this limit, you can use
+
+   png_set_user_limits(png_ptr, width_max, height_max);
+
+to set your own limits, or use width_max = height_max = 0x7fffffffL
+to allow all valid dimensions (libpng may reject some very large images
+anyway because of potential buffer overflow conditions).
+
+You should put this statement after you create the PNG structure and
+before calling png_read_info(), png_read_png(), or png_process_data().
+If you need to retrieve the limits that are being applied, use
+
+   width_max = png_get_user_width_max(png_ptr);
+   height_max = png_get_user_height_max(png_ptr);
+

 Unknown-chunk handling
 
 Now you get to set the way the library processes unknown chunks in the
 Unknown-chunk handling
 
 Now you get to set the way the library processes unknown chunks in the


@@ -308,23 +330,31 @@ behavior is that known chunks will be parsed into information in
 various info_ptr members; unknown chunks will be discarded. To change
 this, you can call:
 
 various info_ptr members; unknown chunks will be discarded. To change
 this, you can call:
 

-    png_set_keep_unknown_chunks(png_ptr, info_ptr, keep,
+    png_set_keep_unknown_chunks(png_ptr, keep,

         chunk_list, num_chunks);
         chunk_list, num_chunks);

-    keep       - 0: do not keep
-                 1: keep only if safe-to-copy
-                 2: keep even if unsafe-to-copy
+    keep       - 0: do not handle as unknown
+                 1: do not keep
+                 2: keep only if safe-to-copy
+                 3: keep even if unsafe-to-copy
+               You can use these definitions:
+                 PNG_HANDLE_CHUNK_AS_DEFAULT   0
+                 PNG_HANDLE_CHUNK_NEVER        1
+                 PNG_HANDLE_CHUNK_IF_SAFE      2
+                 PNG_HANDLE_CHUNK_ALWAYS       3

     chunk_list - list of chunks affected (a byte string,
                  five bytes per chunk, NULL or '\0' if
                  num_chunks is 0)
     num_chunks - number of chunks affected; if 0, all
     chunk_list - list of chunks affected (a byte string,
                  five bytes per chunk, NULL or '\0' if
                  num_chunks is 0)
     num_chunks - number of chunks affected; if 0, all

-                 unknown chunks are affected
+                 unknown chunks are affected.  If nonzero,
+                 only the chunks in the list are affected

 
 Unknown chunks declared in this way will be saved as raw data onto a
 list of png_unknown_chunk structures.  If a chunk that is normally
 known to libpng is named in the list, it will be handled as unknown,
 according to the "keep" directive.  If a chunk is named in successive
 instances of png_set_keep_unknown_chunks(), the final instance will
 
 Unknown chunks declared in this way will be saved as raw data onto a
 list of png_unknown_chunk structures.  If a chunk that is normally
 known to libpng is named in the list, it will be handled as unknown,
 according to the "keep" directive.  If a chunk is named in successive
 instances of png_set_keep_unknown_chunks(), the final instance will

-take precedence.
+take precedence.  The IHDR and IEND chunks should not be named in
+chunk_list; if they are, libpng will process them normally anyway.

 
 The high-level read interface
 
 
 The high-level read interface
 


@@ -379,8 +409,14 @@ where row_pointers is an array of pointers to the pixel data for each row:
 If you know your image size and pixel size ahead of time, you can allocate
 row_pointers prior to calling png_read_png() with
 
 If you know your image size and pixel size ahead of time, you can allocate
 row_pointers prior to calling png_read_png() with
 

+   if (height > PNG_UINT_32_MAX/png_sizeof(png_byte))
+      png_error (png_ptr,
+         "Image is too tall to process in memory");
+   if (width > PNG_UINT_32_MAX/pixel_size)
+      png_error (png_ptr,
+         "Image is too wide to process in memory");

    row_pointers = png_malloc(png_ptr,
    row_pointers = png_malloc(png_ptr,

-      height*sizeof(png_bytep));
+      height*png_sizeof(png_bytep));

    for (int i=0; i<height, i++)
       row_pointers[i]=png_malloc(png_ptr,
          width*pixel_size);
    for (int i=0; i<height, i++)
       row_pointers[i]=png_malloc(png_ptr,
          width*pixel_size);


@@ -2310,7 +2346,6 @@ functions must be modified in the library at compile time.  If you prefer
 to use a different method of allocating and freeing data, you can use
 png_create_read_struct_2() or png_create_write_struct_2() to register
 your own functions as described above.
 to use a different method of allocating and freeing data, you can use
 png_create_read_struct_2() or png_create_write_struct_2() to register
 your own functions as described above.

-

 These functions also provide a void pointer that can be retrieved via
 
     mem_ptr=png_get_mem_ptr(png_ptr);
 These functions also provide a void pointer that can be retrieved via
 
     mem_ptr=png_get_mem_ptr(png_ptr);


@@ -2321,9 +2356,9 @@ Your replacement memory functions must have prototypes as follows:
        png_size_t size);
     void free_fn(png_structp png_ptr, png_voidp ptr);
 
        png_size_t size);
     void free_fn(png_structp png_ptr, png_voidp ptr);
 

-Your malloc_fn() should return NULL in case of failure.  The png_malloc()
-function will call png_error() if it receives a NULL from the system
-memory allocator or from your replacement malloc_fn().
+Your malloc_fn() must return NULL in case of failure.  The png_malloc()
+function will normally call png_error() if it receives a NULL from the
+system memory allocator or from your replacement malloc_fn().

 
 Input/Output in libpng is done through png_read() and png_write(),
 which currently just call fread() and fwrite().  The FILE * is stored in
 
 Input/Output in libpng is done through png_read() and png_write(),
 which currently just call fread() and fwrite().  The FILE * is stored in


@@ -2773,8 +2808,7 @@ For more extensive examples of runtime querying, enabling and disabling
 of optimized features, see contrib/gregbook/readpng2.c in the libpng
 source-code distribution.
 
 of optimized features, see contrib/gregbook/readpng2.c in the libpng
 source-code distribution.
 

-
-VII.  MNG support
+VI.  MNG support

 
 The MNG specification (available at http://www.libpng.org/pub/mng) allows
 certain extensions to PNG for PNG images that are embedded in MNG datastreams.
 
 The MNG specification (available at http://www.libpng.org/pub/mng) allows
 certain extensions to PNG for PNG images that are embedded in MNG datastreams.


@@ -2787,7 +2821,7 @@ png_permit_mng_features() function:
         PNG_FLAG_MNG_EMPTY_PLTE
         PNG_FLAG_MNG_FILTER_64
         PNG_ALL_MNG_FEATURES
         PNG_FLAG_MNG_EMPTY_PLTE
         PNG_FLAG_MNG_FILTER_64
         PNG_ALL_MNG_FEATURES

-   feature_set is a png_32_uint that is the logical AND of
+   feature_set is a png_uint_32 that is the logical AND of

       your mask with the set of MNG features that is
       supported by the version of libpng that you are using.
 
       your mask with the set of MNG features that is
       supported by the version of libpng that you are using.
 


@@ -2799,7 +2833,7 @@ or any other MNG chunks; your application must provide its own support for
 them.  You may wish to consider using libmng (available at
 http://www.libmng.com) instead.
 
 them.  You may wish to consider using libmng (available at
 http://www.libmng.com) instead.
 

-VIII.  Changes to Libpng from version 0.88
+VII.  Changes to Libpng from version 0.88

 
 It should be noted that versions of libpng later than 0.96 are not
 distributed by the original libpng author, Guy Schalnat, nor by
 
 It should be noted that versions of libpng later than 0.96 are not
 distributed by the original libpng author, Guy Schalnat, nor by


@@ -2848,15 +2882,15 @@ application:
 
    png_uint_32 application_vn = PNG_LIBPNG_VER;
 
 
    png_uint_32 application_vn = PNG_LIBPNG_VER;
 

-IX. Y2K Compliance in libpng
+VII. Y2K Compliance in libpng

 
 

-September 18, 2002
+August 15, 2004

 
 Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.
 
 This is your unofficial assurance that libpng from version 0.71 and
 
 Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.
 
 This is your unofficial assurance that libpng from version 0.71 and

-upward through 1.2.5rc3 are Y2K compliant.  It is my belief that earlier
+upward through 1.2.6 are Y2K compliant.  It is my belief that earlier

 versions were also Y2K compliant.
 
 Libpng only has three year fields.  One is a 2-byte unsigned integer that
 versions were also Y2K compliant.
 
 Libpng only has three year fields.  One is a 2-byte unsigned integer that