[libpng17] Support builds with unsupported PNG_TRANSFORM_* values. All of the

PNG_TRANSFORM_* values are always defined in png.h and, because they
are used for both read and write in some cases, it is not reliable
to #if out ones that are totally unsupported. This change adds error
detection in png_read_image() and png_write_image() to do a
png_app_error() if the app requests something that cannot be done
and it adds corresponding code to pngimage.c to handle such options
by not attempting to test them.

ANNOUNCE

@@ -1,5 +1,5 @@
 
-Libpng 1.7.0beta31 - February 5, 2014
+Libpng 1.7.0beta31 - February 6, 2014
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -504,7 +504,7 @@ Version 1.7.0beta30 [February 2, 2014]
     the program by virtue of exhaustively testing all the transforms is
     very slow.
 
-Version 1.7.0beta31 [February 5, 2014]
+Version 1.7.0beta31 [February 6, 2014]
   Make png_read_png() and png_write_png() prototypes in png.h depend
     upon PNG_READ_SUPPORTED and PNG_WRITE_SUPPORTED.
   Removed dependence on !PNG_READ_EXPAND_SUPPORTED for calling
@@ -524,6 +524,14 @@ Version 1.7.0beta31 [February 5, 2014]
     PAETH filtering code from libpng-1.7.0beta24/pngrutil.c. Deleted
     the other instance of "c = b;" which is the one that triggered a
     scan-build warning.
+  Support builds with unsupported PNG_TRANSFORM_* values.  All of the
+    PNG_TRANSFORM_* values are always defined in png.h and, because they
+    are used for both read and write in some cases, it is not reliable
+    to #if out ones that are totally unsupported. This change adds error
+    detection in png_read_image() and png_write_image() to do a
+    png_app_error() if the app requests something that cannot be done
+    and it adds corresponding code to pngimage.c to handle such options
+    by not attempting to test them.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

CHANGES

@@ -4793,7 +4793,7 @@ Version 1.7.0beta30 [February 2, 2014]
     the program by virtue of exhaustively testing all the transforms is
     very slow.
 
-Version 1.7.0beta31 [February 5, 2014]
+Version 1.7.0beta31 [February 6, 2014]
   Make png_read_png() and png_write_png() prototypes in png.h depend
     upon PNG_READ_SUPPORTED and PNG_WRITE_SUPPORTED.
   Removed dependence on !PNG_READ_EXPAND_SUPPORTED for calling
@@ -4813,6 +4813,14 @@ Version 1.7.0beta31 [February 5, 2014]
     PAETH filtering code from libpng-1.7.0beta24/pngrutil.c. Deleted
     the other instance of "c = b;" which is the one that triggered a
     scan-build warning.
+  Support builds with unsupported PNG_TRANSFORM_* values.  All of the
+    PNG_TRANSFORM_* values are always defined in png.h and, because they
+    are used for both read and write in some cases, it is not reliable
+    to #if out ones that are totally unsupported. This change adds error
+    detection in png_read_image() and png_write_image() to do a
+    png_app_error() if the app requests something that cannot be done
+    and it adds corresponding code to pngimage.c to handle such options
+    by not attempting to test them.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

png.h

@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.7.0beta31 - February 5, 2014
+ * libpng version 1.7.0beta31 - February 6, 2014
  * Copyright (c) 1998-2013 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -11,7 +11,7 @@
  * Authors and maintainers:
  *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  *   libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.7.0beta31 - February 5, 2014: Glenn
+ *   libpng versions 0.97, January 1998, through 1.7.0beta31 - February 6, 2014: Glenn
  *   See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -200,7 +200,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.7.0beta31, February 5, 2014, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.7.0beta31, February 6, 2014, are
  * Copyright (c) 2004, 2006-2013 Glenn Randers-Pehrson, and are
  * distributed according to the same disclaimer and license as libpng-1.2.5
  * with the following individual added to the list of Contributing Authors:
@@ -312,7 +312,7 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    February 5, 2014
+ *    February 6, 2014
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
@@ -380,7 +380,7 @@
 /* Version information for png.h - this should match the version in png.c */
 #define PNG_LIBPNG_VER_STRING "1.7.0beta31"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.7.0beta31 - February 5, 2014\n"
+     " libpng version 1.7.0beta31 - February 6, 2014\n"
 
 #define PNG_LIBPNG_VER_SONUM   17
 #define PNG_LIBPNG_VER_DLLNUM  17
@@ -2620,7 +2620,7 @@ PNG_EXPORT(177, void, png_set_invalid, (png_const_structrp png_ptr,
 
 #ifdef PNG_INFO_IMAGE_SUPPORTED
 /* The "params" pointer is currently not used and is for future expansion. */
-#ifdef PNG_READ_SUPPORTED
+#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
 PNG_EXPORT(178, void, png_read_png, (png_structrp png_ptr, png_inforp info_ptr,
     int transforms, png_voidp params));
 #endif

pngread.c

@@ -1001,8 +1001,6 @@ png_read_png(png_structrp png_ptr, png_inforp info_ptr,
                            int transforms,
                            voidp params)
 {
-   int row;
-
    if (png_ptr == NULL || info_ptr == NULL)
       return;
 
@@ -1014,120 +1012,149 @@ png_read_png(png_structrp png_ptr, png_inforp info_ptr,
       png_error(png_ptr, "Image is too high to process with png_read_png()");
 
    /* -------------- image transformations start here ------------------- */
+   /* libpng 1.6.10: add code to cause a png_app_error if a selected TRANSFORM
+    * is not implemented.  This will only happen in de-configured (non-default)
+    * libpng builds.  The results can be unexpected - png_read_png may return
+    * short or mal-formed rows because the transform is skipped.
+    */
 
-#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
    /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
     */
    if (transforms & PNG_TRANSFORM_SCALE_16)
-   {
      /* Added at libpng-1.5.4. "strip_16" produces the same result that it
       * did in earlier versions, while "scale_16" is now more accurate.
       */
+#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
       png_set_scale_16(png_ptr);
-   }
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_SCALE_16 not supported");
 #endif
 
-#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
    /* If both SCALE and STRIP are required pngrtran will effectively cancel the
     * latter by doing SCALE first.  This is ok and allows apps not to check for
     * which is supported to get the right answer.
     */
    if (transforms & PNG_TRANSFORM_STRIP_16)
+#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
       png_set_strip_16(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_16 not supported");
 #endif
 
-#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    /* Strip alpha bytes from the input data without combining with
     * the background (not recommended).
     */
    if (transforms & PNG_TRANSFORM_STRIP_ALPHA)
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
       png_set_strip_alpha(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_ALPHA not supported");
 #endif
 
-#if defined(PNG_READ_PACK_SUPPORTED)
    /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
     * byte into separate bytes (useful for paletted and grayscale images).
     */
    if (transforms & PNG_TRANSFORM_PACKING)
+#ifdef PNG_READ_PACK_SUPPORTED
       png_set_packing(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
 #endif
 
-#ifdef PNG_READ_PACKSWAP_SUPPORTED
    /* Change the order of packed pixels to least significant bit first
     * (not useful if you are using png_set_packing).
     */
    if (transforms & PNG_TRANSFORM_PACKSWAP)
+#ifdef PNG_READ_PACKSWAP_SUPPORTED
       png_set_packswap(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
 #endif
 
-#ifdef PNG_READ_EXPAND_SUPPORTED
    /* Expand paletted colors into true RGB triplets
     * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
     * Expand paletted or RGB images with transparency to full alpha
     * channels so the data will be available as RGBA quartets.
     */
    if (transforms & PNG_TRANSFORM_EXPAND)
-      if ((png_ptr->bit_depth < 8) ||
+#ifdef PNG_READ_EXPAND_SUPPORTED
-          (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ||
-          (info_ptr->valid & PNG_INFO_tRNS))
       png_set_expand(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND not supported");
 #endif
 
    /* We don't handle background color or gamma transformation or quantizing.
     */
 
-#ifdef PNG_READ_INVERT_SUPPORTED
    /* Invert monochrome files to have 0 as white and 1 as black
     */
    if (transforms & PNG_TRANSFORM_INVERT_MONO)
+#ifdef PNG_READ_INVERT_SUPPORTED
       png_set_invert_mono(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
 #endif
 
-#ifdef PNG_READ_SHIFT_SUPPORTED
    /* If you want to shift the pixel values from the range [0,255] or
     * [0,65535] to the original [0,7] or [0,31], or whatever range the
     * colors were originally in:
     */
-   if ((transforms & PNG_TRANSFORM_SHIFT) && (info_ptr->valid & PNG_INFO_sBIT))
+   if (transforms & PNG_TRANSFORM_SHIFT)
+#ifdef PNG_READ_SHIFT_SUPPORTED
+      if (info_ptr->valid & PNG_INFO_sBIT)
          png_set_shift(png_ptr, &info_ptr->sig_bit);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
 #endif
 
-#ifdef PNG_READ_BGR_SUPPORTED
    /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
    if (transforms & PNG_TRANSFORM_BGR)
+#ifdef PNG_READ_BGR_SUPPORTED
       png_set_bgr(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
 #endif
 
-#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
    /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
    if (transforms & PNG_TRANSFORM_SWAP_ALPHA)
+#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
       png_set_swap_alpha(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
 #endif
 
-#ifdef PNG_READ_SWAP_SUPPORTED
    /* Swap bytes of 16-bit files to least significant byte first */
    if (transforms & PNG_TRANSFORM_SWAP_ENDIAN)
+#ifdef PNG_READ_SWAP_SUPPORTED
       png_set_swap(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
 #endif
 
 /* Added at libpng-1.2.41 */
-#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
    /* Invert the alpha channel from opacity to transparency */
    if (transforms & PNG_TRANSFORM_INVERT_ALPHA)
+#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
       png_set_invert_alpha(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
 #endif
 
 /* Added at libpng-1.2.41 */
-#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /* Expand grayscale image to RGB */
    if (transforms & PNG_TRANSFORM_GRAY_TO_RGB)
+#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
       png_set_gray_to_rgb(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_GRAY_TO_RGB not supported");
 #endif
 
 /* Added at libpng-1.5.4 */
-#ifdef PNG_READ_EXPAND_16_SUPPORTED
    if (transforms & PNG_TRANSFORM_EXPAND_16)
+#ifdef PNG_READ_EXPAND_16_SUPPORTED
       png_set_expand_16(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_EXPAND_16 not supported");
 #endif
 
    /* We don't handle adding filler bytes */
@@ -1150,16 +1177,17 @@ png_read_png(png_structrp png_ptr, png_inforp info_ptr,
    {
       png_uint_32 iptr;
 
-      info_ptr->row_pointers = (png_bytepp)png_malloc(png_ptr,
+      info_ptr->row_pointers = png_voidcast(png_bytepp, png_malloc(png_ptr,
-          info_ptr->height * (sizeof (png_bytep)));
+          info_ptr->height * (sizeof (png_bytep))));
+
       for (iptr=0; iptr<info_ptr->height; iptr++)
          info_ptr->row_pointers[iptr] = NULL;
 
       info_ptr->free_me |= PNG_FREE_ROWS;
 
-      for (row = 0; row < (int)info_ptr->height; row++)
+      for (iptr = 0; iptr < info_ptr->height; iptr++)
-         info_ptr->row_pointers[row] = (png_bytep)png_malloc(png_ptr,
+         info_ptr->row_pointers[iptr] = png_voidcast(png_bytep,
-            png_get_rowbytes(png_ptr, info_ptr));
+            png_malloc(png_ptr, info_ptr->rowbytes));
    }
 
    png_read_image(png_ptr, info_ptr->row_pointers);
@@ -1168,9 +1196,7 @@ png_read_png(png_structrp png_ptr, png_inforp info_ptr,
    /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
    png_read_end(png_ptr, info_ptr);
 
-   PNG_UNUSED(transforms)   /* Quiet compiler warnings */
    PNG_UNUSED(params)
-
 }
 #endif /* PNG_INFO_IMAGE_SUPPORTED */
 #endif /* PNG_SEQUENTIAL_READ_SUPPORTED */

pngwrite.c

@@ -1532,81 +1532,117 @@ png_write_png(png_structrp png_ptr, png_inforp info_ptr,
    if (png_ptr == NULL || info_ptr == NULL)
       return;
 
+   if ((info_ptr->valid & PNG_INFO_IDAT) == 0)
+   {
+      png_app_error(png_ptr, "no rows for png_write_image to write");
+      return;
+   }
+
    /* Write the file header information. */
    png_write_info(png_ptr, info_ptr);
 
    /* ------ these transformations don't touch the info structure ------- */
 
-#ifdef PNG_WRITE_INVERT_SUPPORTED
    /* Invert monochrome pixels */
    if (transforms & PNG_TRANSFORM_INVERT_MONO)
+#ifdef PNG_WRITE_INVERT_SUPPORTED
       png_set_invert_mono(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
 #endif
 
-#ifdef PNG_WRITE_SHIFT_SUPPORTED
    /* Shift the pixels up to a legal bit depth and fill in
     * as appropriate to correctly scale the image.
     */
-   if ((transforms & PNG_TRANSFORM_SHIFT)
+   if (transforms & PNG_TRANSFORM_SHIFT)
-       && (info_ptr->valid & PNG_INFO_sBIT))
+#ifdef PNG_WRITE_SHIFT_SUPPORTED
+      if (info_ptr->valid & PNG_INFO_sBIT)
          png_set_shift(png_ptr, &info_ptr->sig_bit);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
 #endif
 
-#ifdef PNG_WRITE_PACK_SUPPORTED
    /* Pack pixels into bytes */
    if (transforms & PNG_TRANSFORM_PACKING)
+#ifdef PNG_WRITE_PACK_SUPPORTED
       png_set_packing(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
 #endif
 
-#ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
    /* Swap location of alpha bytes from ARGB to RGBA */
    if (transforms & PNG_TRANSFORM_SWAP_ALPHA)
+#ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
       png_set_swap_alpha(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
 #endif
 
+   /* Remove a filler (X) from XRGB/RGBX/AG/GA into to convert it into
+    * RGB, note that the code expects the input color type to be G or RGB; no
+    * alpha channel.
+    */
+   if (transforms &
+      (PNG_TRANSFORM_STRIP_FILLER_AFTER|PNG_TRANSFORM_STRIP_FILLER_BEFORE))
+   {
 #ifdef PNG_WRITE_FILLER_SUPPORTED
-   /* Pack XRGB/RGBX/ARGB/RGBA into RGB (4 channels -> 3 channels) */
       if (transforms & PNG_TRANSFORM_STRIP_FILLER_AFTER)
+      {
+         if (transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE)
+            png_app_error(png_ptr,
+               "PNG_TRANSFORM_STRIP_FILLER: BEFORE+AFTER not supported");
+
+         /* Continue if ignored - this is the pre-1.6.10 behavior */
          png_set_filler(png_ptr, 0, PNG_FILLER_AFTER);
+      }
 
       else if (transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE)
          png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_FILLER not supported");
 #endif
+   }
 
-#ifdef PNG_WRITE_BGR_SUPPORTED
    /* Flip BGR pixels to RGB */
    if (transforms & PNG_TRANSFORM_BGR)
+#ifdef PNG_WRITE_BGR_SUPPORTED
       png_set_bgr(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
 #endif
 
-#ifdef PNG_WRITE_SWAP_SUPPORTED
    /* Swap bytes of 16-bit files to most significant byte first */
    if (transforms & PNG_TRANSFORM_SWAP_ENDIAN)
+#ifdef PNG_WRITE_SWAP_SUPPORTED
       png_set_swap(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
 #endif
 
-#ifdef PNG_WRITE_PACKSWAP_SUPPORTED
    /* Swap bits of 1, 2, 4 bit packed pixel formats */
    if (transforms & PNG_TRANSFORM_PACKSWAP)
+#ifdef PNG_WRITE_PACKSWAP_SUPPORTED
       png_set_packswap(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
 #endif
 
-#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
    /* Invert the alpha channel from opacity to transparency */
    if (transforms & PNG_TRANSFORM_INVERT_ALPHA)
+#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
       png_set_invert_alpha(png_ptr);
+#else
+      png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
 #endif
 
    /* ----------------------- end of transformations ------------------- */
 
    /* Write the bits */
-   if (info_ptr->valid & PNG_INFO_IDAT)
    png_write_image(png_ptr, info_ptr->row_pointers);
 
    /* It is REQUIRED to call this to finish writing the rest of the file */
    png_write_end(png_ptr, info_ptr);
 
-   PNG_UNUSED(transforms)   /* Quiet compiler warnings */
    PNG_UNUSED(params)
 }
 #endif