diff --git a/ANNOUNCE b/ANNOUNCE
index e8ed397e3..29db5aca7 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.4.2rc01 - April 10, 2010
+Libpng 1.4.2rc02 - April 16, 2010
 
 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.
@@ -9,20 +9,20 @@ Files available for download:
 Source files with LF line endings (for Unix/Linux) and with a
 "configure" script
 
-   1.4.2rc01.tar.xz (LZMA-compressed, recommended)
-   1.4.2rc01.tar.gz
-   1.4.2rc01.tar.bz2
+   1.4.2rc02.tar.xz (LZMA-compressed, recommended)
+   1.4.2rc02.tar.gz
+   1.4.2rc02.tar.bz2
 
 Source files with CRLF line endings (for Windows), without the
 "configure" script
 
-   lp142r01.zip
-   lp142r01.7z
+   lp142r02.zip
+   lp142r02.7z
 
 Other information:
 
-   1.4.2rc01-README.txt
-   1.4.2rc01-LICENSE.txt
+   1.4.2rc02-README.txt
+   1.4.2rc02-LICENSE.txt
 
 Changes since the last public release (1.4.1):
 
@@ -31,6 +31,14 @@ version 1.4.2beta01 [April 1, 2010]
   Conditionally compile an "else" statement in png_decompress_chunk().
 
 version 1.4.2rc01 [April 10, 2010]
+  No changes.
+
+version 1.4.2rc02 [April 16, 2010]
+  Documented the fact that png_set_dither() was disabled since libpng-1.4.0.
+  Reenabled png_set_dither() but renamed it to png_set_quantize() to reflect
+    more accurately what it actually does.  At the same time, renamed
+    the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros to
+    PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 87eb16292..a1cea8ffd 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2054,7 +2054,7 @@ version 1.4.0beta46 [December 10, 2008]
     PNG_TRANSFORM_STRIP_FILLER (Jim Barry).
 
 version 1.4.0beta47 [December 15, 2008]
-  Support for dithering was removed by default, because it has never
+  Support for dithering was disabled by default, because it has never
     been well tested and doesn't work very well.  The code has not
     been removed, however, and can be enabled by building libpng with
     PNG_READ_DITHER_SUPPORTED defined.
@@ -2541,7 +2541,15 @@ version 1.4.2beta01 [April 1, 2010]
   Conditionally compile an "else" statement in png_decompress_chunk().
   Restored the macro definition of png_check_sig().
 
-version 1.4.2rc01 [April 14, 2010]
+version 1.4.2rc01 [April 10, 2010]
+  No changes.
+
+version 1.4.2rc02 [April 16, 2010]
+  Documented the fact that png_set_dither() was disabled since libpng-1.4.0.
+  Reenabled png_set_dither() but renamed it to png_set_quantize() to reflect
+    more accurately what it actually does.  At the same time, renamed
+    the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros to
+    PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/example.c b/example.c
index b79d8413c..8d06182c0 100644
--- a/example.c
+++ b/example.c
@@ -160,7 +160,7 @@ void read_png(FILE *fp, unsigned int sig_read)  /* File is already open */
     * If you have enough memory to read in the entire image at once,
     * and you need to specify only transforms that can be controlled
     * with one of the PNG_TRANSFORM_* bits (this presently excludes
-    * dithering, filling, setting background, and doing gamma
+    * quantizing, filling, setting background, and doing gamma
     * adjustment), then you can read the entire image (including
     * pixels) into the info structure with this call:
     */
@@ -271,8 +271,8 @@ void read_png(FILE *fp, unsigned int sig_read)  /* File is already open */
          png_set_gamma(png_ptr, screen_gamma, 0.45455);
    }
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-   /* Dither RGB files down to 8 bit palette or reduce palettes
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   /* Quantize RGB files down to 8 bit palette or reduce palettes
     * to the number of colors available on your screen.
     */
    if (color_type & PNG_COLOR_MASK_COLOR)
@@ -283,10 +283,11 @@ void read_png(FILE *fp, unsigned int sig_read)  /* File is already open */
       /* This reduces the image to the application supplied palette */
       if (/* We have our own palette */)
       {
-         /* An array of colors to which the image should be dithered */
+         /* An array of colors to which the image should be quantized */
          png_color std_color_cube[MAX_SCREEN_COLORS];
 
-         png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
+         /* Prior to libpng-1.4.2, this was png_set_dither(). */
+         png_set_quantize(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
             MAX_SCREEN_COLORS, NULL, 0);
       }
       /* This reduces the image to the palette supplied in the file */
@@ -296,11 +297,11 @@ void read_png(FILE *fp, unsigned int sig_read)  /* File is already open */
 
          png_get_hIST(png_ptr, info_ptr, &histogram);
 
-         png_set_dither(png_ptr, palette, num_palette,
+         png_set_quantize(png_ptr, palette, num_palette,
                         max_screen_colors, histogram, 0);
       }
    }
-#endif /* PNG_READ_DITHER_SUPPORTED */
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
 
    /* Invert monochrome files to have 0 as white and 1 as black */
    png_set_invert_mono(png_ptr);
diff --git a/libpng-1.4.2rc01.txt b/libpng-1.4.2rc01.txt
index 6b608e764..d9cdd38f8 100644
--- a/libpng-1.4.2rc01.txt
+++ b/libpng-1.4.2rc01.txt
@@ -1,6 +1,6 @@
 libpng.txt - A description on how to use and modify libpng
 
- libpng version 1.4.2rc02 - April 14, 2010
+ libpng version 1.4.2rc02 - April 16, 2010
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2009 Glenn Randers-Pehrson
@@ -11,7 +11,7 @@ libpng.txt - A description on how to use and modify libpng
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.4.2rc02 - April 14, 2010
+ libpng versions 0.97, January 1998, through 1.4.2rc02 - April 16, 2010
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2009 Glenn Randers-Pehrson
 
@@ -475,7 +475,7 @@ you want to do are limited to the following set:
                                 to RGB (or GA to RGBA)
 
 (This excludes setting a background color, doing gamma transformation,
-dithering, and setting filler.)  If this is the case, simply do this:
+quantizing, and setting filler.)  If this is the case, simply do this:
 
     png_read_png(png_ptr, info_ptr, png_transforms, NULL)
 
@@ -1159,6 +1159,40 @@ recommended that PNG viewers support gamma correction.
    else
       png_set_gamma(png_ptr, screen_gamma, 0.45455);
 
+If you need to reduce an RGB file to a paletted file, or if a paletted
+file has more entries then will fit on your screen, png_set_quantize()
+will do that.  Note that this is a simple match dither that merely
+finds the closest color available.  This should work fairly well with
+optimized palettes, and fairly badly with linear color cubes.  If you
+pass a palette that is larger then maximum_colors, the file will
+reduce the number of colors in the palette so it will fit into
+maximum_colors.  If there is a histogram, it will use it to make
+more intelligent choices when reducing the palette.  If there is no
+histogram, it may not do as good a job.
+
+   if (color_type & PNG_COLOR_MASK_COLOR)
+   {
+      if (png_get_valid(png_ptr, info_ptr,
+         PNG_INFO_PLTE))
+      {
+         png_uint_16p histogram = NULL;
+
+         png_get_hIST(png_ptr, info_ptr,
+            &histogram);
+         png_set_quantize(png_ptr, palette, num_palette,
+            max_screen_colors, histogram, 1);
+      }
+      else
+      {
+         png_color std_color_cube[MAX_SCREEN_COLORS] =
+            { ... colors ... };
+
+         png_set_quantize(png_ptr, std_color_cube,
+            MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
+            NULL,0);
+      }
+   }
+
 PNG files describe monochrome as black being zero and white being one.
 The following code will reverse this (make black be one and white be
 zero):
@@ -3105,10 +3139,14 @@ The png_zalloc() and png_zfree() functions are no longer exported.
 The png_zalloc() function no longer zeroes out the memory that it
 allocates.
 
-Support for dithering was removed by default, because it has never
-been well tested and doesn't work very well.  The code has not
-been removed, however, and can be enabled by building libpng with
-PNG_READ_DITHER_SUPPORTED defined.
+Support for dithering was disabled by default in libpng-1.4.0, because
+been well tested and doesn't actually "dither".  The code was not
+removed, however, and could be enabled by building libpng with
+PNG_READ_DITHER_SUPPORTED defined.  In libpng-1.4.2, this support
+was reenabled, but the function was renamed png_set_quantize() to
+reflect more accurately what it actually does.  At the same time,
+the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to
+PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS.
 
 We removed the trailing '.' from the warning and error messages.
 
@@ -3250,7 +3288,7 @@ Other rules can be inferred by inspecting the libpng source.
 
 XIII. Y2K Compliance in libpng
 
-April 14, 2010
+April 16, 2010
 
 Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.
diff --git a/libpng.3 b/libpng.3
index f8320aeca..1b4567269 100644
--- a/libpng.3
+++ b/libpng.3
@@ -1,4 +1,4 @@
-.TH LIBPNG 3 "April 14, 2010"
+.TH LIBPNG 3 "April 16, 2010"
 .SH NAME
 libpng \- Portable Network Graphics (PNG) Reference Library 1.4.2rc02
 .SH SYNOPSIS
@@ -454,7 +454,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.2rc02
 
 \fI\fB
 
-\fBvoid png_set_dither (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_dither\fP\fB);\fP
+\fBvoid png_set_quantize (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_quantize\fP\fB);\fP
 
 \fI\fB
 
@@ -785,7 +785,7 @@ Following is a copy of the libpng.txt file that accompanies libpng.
 .SH LIBPNG.TXT
 libpng.txt - A description on how to use and modify libpng
 
- libpng version 1.4.2rc02 - April 14, 2010
+ libpng version 1.4.2rc02 - April 16, 2010
  Updated and distributed by Glenn Randers-Pehrson
  <glennrp at users.sourceforge.net>
  Copyright (c) 1998-2009 Glenn Randers-Pehrson
@@ -796,7 +796,7 @@ libpng.txt - A description on how to use and modify libpng
 
  Based on:
 
- libpng versions 0.97, January 1998, through 1.4.2rc02 - April 14, 2010
+ libpng versions 0.97, January 1998, through 1.4.2rc02 - April 16, 2010
  Updated and distributed by Glenn Randers-Pehrson
  Copyright (c) 1998-2009 Glenn Randers-Pehrson
 
@@ -1260,7 +1260,7 @@ you want to do are limited to the following set:
                                 to RGB (or GA to RGBA)
 
 (This excludes setting a background color, doing gamma transformation,
-dithering, and setting filler.)  If this is the case, simply do this:
+quantizing, and setting filler.)  If this is the case, simply do this:
 
     png_read_png(png_ptr, info_ptr, png_transforms, NULL)
 
@@ -1944,6 +1944,40 @@ recommended that PNG viewers support gamma correction.
    else
       png_set_gamma(png_ptr, screen_gamma, 0.45455);
 
+If you need to reduce an RGB file to a paletted file, or if a paletted
+file has more entries then will fit on your screen, png_set_quantize()
+will do that.  Note that this is a simple match dither that merely
+finds the closest color available.  This should work fairly well with
+optimized palettes, and fairly badly with linear color cubes.  If you
+pass a palette that is larger then maximum_colors, the file will
+reduce the number of colors in the palette so it will fit into
+maximum_colors.  If there is a histogram, it will use it to make
+more intelligent choices when reducing the palette.  If there is no
+histogram, it may not do as good a job.
+
+   if (color_type & PNG_COLOR_MASK_COLOR)
+   {
+      if (png_get_valid(png_ptr, info_ptr,
+         PNG_INFO_PLTE))
+      {
+         png_uint_16p histogram = NULL;
+
+         png_get_hIST(png_ptr, info_ptr,
+            &histogram);
+         png_set_quantize(png_ptr, palette, num_palette,
+            max_screen_colors, histogram, 1);
+      }
+      else
+      {
+         png_color std_color_cube[MAX_SCREEN_COLORS] =
+            { ... colors ... };
+
+         png_set_quantize(png_ptr, std_color_cube,
+            MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
+            NULL,0);
+      }
+   }
+
 PNG files describe monochrome as black being zero and white being one.
 The following code will reverse this (make black be one and white be
 zero):
@@ -3890,10 +3924,14 @@ The png_zalloc() and png_zfree() functions are no longer exported.
 The png_zalloc() function no longer zeroes out the memory that it
 allocates.
 
-Support for dithering was removed by default, because it has never
-been well tested and doesn't work very well.  The code has not
-been removed, however, and can be enabled by building libpng with
-PNG_READ_DITHER_SUPPORTED defined.
+Support for dithering was disabled by default in libpng-1.4.0, because
+been well tested and doesn't actually "dither".  The code was not
+removed, however, and could be enabled by building libpng with
+PNG_READ_DITHER_SUPPORTED defined.  In libpng-1.4.2, this support
+was reenabled, but the function was renamed png_set_quantize() to
+reflect more accurately what it actually does.  At the same time,
+the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to
+PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS.
 
 We removed the trailing '.' from the warning and error messages.
 
@@ -4035,7 +4073,7 @@ Other rules can be inferred by inspecting the libpng source.
 
 .SH XIII. Y2K Compliance in libpng
 
-April 14, 2010
+April 16, 2010
 
 Since the PNG Development group is an ad-hoc body, we can't make
 an official declaration.
@@ -4275,7 +4313,7 @@ possible without all of you.
 
 Thanks to Frank J. T. Wojcik for helping with the documentation.
 
-Libpng version 1.4.2rc02 - April 14, 2010:
+Libpng version 1.4.2rc02 - April 16, 2010:
 Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
 Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
 
@@ -4298,7 +4336,7 @@ this sentence.
 
 This code is released under the libpng license.
 
-libpng versions 1.2.6, August 15, 2004, through 1.4.2rc02, April 14, 2010, are
+libpng versions 1.2.6, August 15, 2004, through 1.4.2rc02, April 16, 2010, are
 Copyright (c) 2004,2006-2007 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
@@ -4397,7 +4435,7 @@ certification mark of the Open Source Initiative.
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-April 14, 2010
+April 16, 2010
 
 .\" end of man page
 
diff --git a/libpngpf.3 b/libpngpf.3
index 1feca930a..a926802ca 100644
--- a/libpngpf.3
+++ b/libpngpf.3
@@ -1,6 +1,6 @@
-.TH LIBPNGPF 3 "April 10, 2010"
+.TH LIBPNGPF 3 "April 16, 2010"
 .SH NAME
-libpng \- Portable Network Graphics (PNG) Reference Library 1.4.2rc01
+libpng \- Portable Network Graphics (PNG) Reference Library 1.4.2rc02
 (private functions)
 .SH SYNOPSIS
 \fB#include <png.h>\fP
@@ -147,7 +147,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.2rc01
 
 \fI\fB
 
-\fBvoid png_do_dither (png_row_infop \fP\fIrow_info\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fP\fIpalette_lookup\fP\fB, png_bytep \fIdither_lookup\fP\fB);\fP
+\fBvoid png_do_quantize (png_row_infop \fP\fIrow_info\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fP\fIpalette_lookup\fP\fB, png_bytep \fIquantize_lookup\fP\fB);\fP
 
 \fI\fB
 
diff --git a/png.h b/png.h
index 5238ba648..a72d5d534 100644
--- a/png.h
+++ b/png.h
@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.4.2rc01 - April 10, 2010
+ * libpng version 1.4.2rc02 - April 16, 2010
  * Copyright (c) 1998-2010 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 1.4.2rc01 - April 10, 2010: Glenn
+ *  libpng versions 0.97, January 1998, through 1.4.2rc02 - April 16, 2010: Glenn
  *  See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -171,7 +171,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.4.2rc01, April 10, 2010, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.4.2rc02, April 16, 2010, are
  * Copyright (c) 2004, 2006-2010 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:
@@ -283,13 +283,13 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    April 10, 2010
+ *    April 16, 2010
  *
  *    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 1.4.2rc01 are Y2K compliant.  It is my belief that earlier
+ *    upward through 1.4.2rc02 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
@@ -345,9 +345,9 @@
  */
 
 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.4.2rc01"
+#define PNG_LIBPNG_VER_STRING "1.4.2rc02"
 #define PNG_HEADER_VERSION_STRING \
-   " libpng version 1.4.2rc01 - April 10, 2010\n"
+   " libpng version 1.4.2rc02 - April 16, 2010\n"
 
 #define PNG_LIBPNG_VER_SONUM   14
 #define PNG_LIBPNG_VER_DLLNUM  14
@@ -360,7 +360,7 @@
  * PNG_LIBPNG_VER_STRING, omitting any leading zero:
  */
 
-#define PNG_LIBPNG_VER_BUILD  01
+#define PNG_LIBPNG_VER_BUILD  02
 
 /* Release Status */
 #define PNG_LIBPNG_BUILD_ALPHA    1
@@ -1333,13 +1333,13 @@ struct png_struct_def
    png_uint_16 offset_table_count_free PNG_DEPSTRUCT;
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-   png_bytep palette_lookup PNG_DEPSTRUCT; /* lookup table for dithering */
-   png_bytep dither_index PNG_DEPSTRUCT;   /* index translation for palette
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   png_bytep palette_lookup PNG_DEPSTRUCT; /* lookup table for quantizing */
+   png_bytep quantize_index PNG_DEPSTRUCT; /* index translation for palette
                                               files */
 #endif
 
-#if defined(PNG_READ_DITHER_SUPPORTED) || defined(PNG_hIST_SUPPORTED)
+#if defined(PNG_READ_QUANTIZE_SUPPORTED) || defined(PNG_hIST_SUPPORTED)
    png_uint_16p hist PNG_DEPSTRUCT;                /* histogram */
 #endif
 
@@ -1423,9 +1423,9 @@ struct png_struct_def
    png_bytep big_row_buf PNG_DEPSTRUCT;         /* buffer to save current
                                                    (unfiltered) row */
 
-#ifdef PNG_READ_DITHER_SUPPORTED
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
 /* The following three members were added at version 1.0.14 and 1.2.4 */
-   png_bytep dither_sort PNG_DEPSTRUCT;            /* working sort array */
+   png_bytep quantize_sort PNG_DEPSTRUCT;          /* working sort array */
    png_bytep index_to_palette PNG_DEPSTRUCT;       /* where the original
                                                      index currently is
                                                      in the palette */
@@ -1469,7 +1469,7 @@ struct png_struct_def
 /* This triggers a compiler error in png.c, if png.c and png.h
  * do not agree upon the version number.
  */
-typedef png_structp version_1_4_2rc01;
+typedef png_structp version_1_4_2rc02;
 
 typedef png_struct FAR * FAR * png_structpp;
 
@@ -1716,14 +1716,16 @@ extern PNG_EXPORT(void,png_set_background) PNGARG((png_structp png_ptr,
 extern PNG_EXPORT(void,png_set_strip_16) PNGARG((png_structp png_ptr));
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-/* Turn on dithering, and reduce the palette to the number of colors
- * available.
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+/* Turn on quantizing, and reduce the palette to the number of colors
+ * available.  Prior to libpng-1.4.2, this was png_set_dither().
  */
-extern PNG_EXPORT(void,png_set_dither) PNGARG((png_structp png_ptr,
+extern PNG_EXPORT(void,png_set_quantize) PNGARG((png_structp png_ptr,
    png_colorp palette, int num_palette, int maximum_colors,
-   png_uint_16p histogram, int full_dither));
+   png_uint_16p histogram, int full_quantize));
 #endif
+/* This migration aid will be removed from libpng-1.5.0 */
+#define png_set_dither png_set_quantize
 
 #ifdef PNG_READ_GAMMA_SUPPORTED
 /* Handle gamma correction. Screen_gamma=(display_exponent) */
diff --git a/pngconf.h b/pngconf.h
index 3efbf8e07..d6669f2e3 100644
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,7 +1,7 @@
 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.4.2rc01 - April 10, 2010
+ * libpng version 1.4.2rc02 - April 16, 2010
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1998-2010 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -391,18 +391,32 @@
 
 /* Other defines for things like memory and the like can go here.  */
 
-/* This controls how fine the dithering gets.  As this allocates
+/* This controls how fine the quantizing gets.  As this allocates
  * a largish chunk of memory (32K), those who are not as concerned
- * with dithering quality can decrease some or all of these.
+ * with quantizing quality can decrease some or all of these.
  */
-#ifndef PNG_DITHER_RED_BITS
-#  define PNG_DITHER_RED_BITS 5
+
+/* Prior to libpng-1.4.2, these were PNG_DITHER_*_BITS
+ * These migration aids will be removed from libpng-1.5.0.
+ */
+#ifdef PNG_DITHER_RED_BITS
+#  define PNG_QUANTIZE_RED_BITS PNG_DITHER_RED_BITS
 #endif
-#ifndef PNG_DITHER_GREEN_BITS
-#  define PNG_DITHER_GREEN_BITS 5
+#ifdef PNG_DITHER_GREEN_BITS
+#  define PNG_QUANTIZE_GREEN_BITS PNG_DITHER_GREEN_BITS
 #endif
-#ifndef PNG_DITHER_BLUE_BITS
-#  define PNG_DITHER_BLUE_BITS 5
+#ifdef PNG_DITHER_BLUE_BITS
+#  define PNG_QUANTIZE_BLUE_BITS PNG_DITHER_BLUE_BITS
+#endif
+
+#ifndef PNG_QUANTIZE_RED_BITS
+#  define PNG_QUANTIZE_RED_BITS 5
+#endif
+#ifndef PNG_QUANTIZE_GREEN_BITS
+#  define PNG_QUANTIZE_GREEN_BITS 5
+#endif
+#ifndef PNG_QUANTIZE_BLUE_BITS
+#  define PNG_QUANTIZE_BLUE_BITS 5
 #endif
 
 /* This controls how fine the gamma correction becomes when you
@@ -499,11 +513,10 @@
 #  ifndef PNG_NO_READ_INVERT
 #    define PNG_READ_INVERT_SUPPORTED
 #  endif
-#if 0 /* removed from libpng-1.4.0 */
-#  ifndef PNG_NO_READ_DITHER
-#    define PNG_READ_DITHER_SUPPORTED
+#  ifndef PNG_NO_READ_QUANTIZE
+     /* Prior to libpng-1.4.0 this was PNG_READ_DITHER_SUPPORTED */
+#    define PNG_READ_QUANTIZE_SUPPORTED
 #  endif
-#endif /* 0 */
 #  ifndef PNG_NO_READ_BACKGROUND
 #    define PNG_READ_BACKGROUND_SUPPORTED
 #  endif
diff --git a/pngpriv.h b/pngpriv.h
index db1dc991a..e37f55c0a 100644
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -1,7 +1,7 @@
 
 /* pngpriv.h - private declarations for use inside libpng
  *
- * libpng version 1.4.2rc01 - April 10, 2010
+ * libpng version 1.4.2rc02 - April 16, 2010
  * For conditions of distribution and use, see copyright notice in png.h
  * Copyright (c) 1998-2010 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -106,7 +106,7 @@
 #define PNG_SHIFT               0x0008
 #define PNG_SWAP_BYTES          0x0010
 #define PNG_INVERT_MONO         0x0020
-#define PNG_DITHER              0x0040
+#define PNG_QUANTIZE            0x0040 /* formerly PNG_DITHER */
 #define PNG_BACKGROUND          0x0080
 #define PNG_BACKGROUND_EXPAND   0x0100
                           /*    0x0200 unused */
@@ -588,9 +588,9 @@ PNG_EXTERN void png_do_invert PNGARG((png_row_infop row_info, png_bytep row));
 PNG_EXTERN void png_do_chop PNGARG((png_row_infop row_info, png_bytep row));
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-PNG_EXTERN void png_do_dither PNGARG((png_row_infop row_info,
-   png_bytep row, png_bytep palette_lookup, png_bytep dither_lookup));
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+PNG_EXTERN void png_do_quantize PNGARG((png_row_infop row_info,
+   png_bytep row, png_bytep palette_lookup, png_bytep quantize_lookup));
 
 #  ifdef PNG_CORRECT_PALETTE_SUPPORTED
 PNG_EXTERN void png_correct_palette PNGARG((png_structp png_ptr,
diff --git a/pngread.c b/pngread.c
index 0b19e7887..1e3c7bf33 100644
--- a/pngread.c
+++ b/pngread.c
@@ -1,7 +1,7 @@
 
 /* pngread.c - read a PNG file
  *
- * Last changed in libpng 1.4.1 [April 10, 2010]
+ * Last changed in libpng 1.4.1 [April 16, 2010]
  * Copyright (c) 1998-2010 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.)
@@ -1080,9 +1080,9 @@ png_read_destroy(png_structp png_ptr, png_infop info_ptr,
    png_free(png_ptr, png_ptr->big_row_buf);
    png_free(png_ptr, png_ptr->prev_row);
    png_free(png_ptr, png_ptr->chunkdata);
-#ifdef PNG_READ_DITHER_SUPPORTED
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
    png_free(png_ptr, png_ptr->palette_lookup);
-   png_free(png_ptr, png_ptr->dither_index);
+   png_free(png_ptr, png_ptr->quantize_index);
 #endif
 #ifdef PNG_READ_GAMMA_SUPPORTED
    png_free(png_ptr, png_ptr->gamma_table);
@@ -1257,7 +1257,7 @@ png_read_png(png_structp png_ptr, png_infop info_ptr,
          png_set_expand(png_ptr);
 #endif
 
-   /* We don't handle background color or gamma transformation or dithering.
+   /* We don't handle background color or gamma transformation or quantizing.
     */
 
 #ifdef PNG_READ_INVERT_SUPPORTED
diff --git a/pngrtran.c b/pngrtran.c
index 497f72313..44e895a9f 100644
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -1,7 +1,7 @@
 
 /* pngrtran.c - transforms the data in a row for PNG readers
  *
- * Last changed in libpng 1.4.1 [April 14, 2010]
+ * Last changed in libpng 1.4.1 [April 16, 2010]
  * Copyright (c) 1998-2010 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.)
@@ -141,13 +141,13 @@ png_set_strip_alpha(png_structp png_ptr)
 }
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-/* Dither file to 8 bit.  Supply a palette, the current number
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+/* Quantize file to 8 bit.  Supply a palette, the current number
  * of elements in the palette, the maximum number of elements
  * allowed, and a histogram if possible.  If the current number
  * of colors is greater then the maximum number, the palette will be
- * modified to fit in the maximum number.  "full_dither" indicates
- * whether we need a dithering cube set up for RGB images, or if we
+ * modified to fit in the maximum number.  "full_quantize" indicates
+ * whether we need a quantizeing cube set up for RGB images, or if we
  * simply are reducing the number of colors in a paletted image.
  */
 
@@ -161,24 +161,24 @@ typedef png_dsort FAR *       png_dsortp;
 typedef png_dsort FAR * FAR * png_dsortpp;
 
 void PNGAPI
-png_set_dither(png_structp png_ptr, png_colorp palette,
+png_set_quantize(png_structp png_ptr, png_colorp palette,
    int num_palette, int maximum_colors, png_uint_16p histogram,
-   int full_dither)
+   int full_quantize)
 {
-   png_debug(1, "in png_set_dither");
+   png_debug(1, "in png_set_quantize");
 
    if (png_ptr == NULL)
       return;
-   png_ptr->transformations |= PNG_DITHER;
+   png_ptr->transformations |= PNG_QUANTIZE;
 
-   if (!full_dither)
+   if (!full_quantize)
    {
       int i;
 
-      png_ptr->dither_index = (png_bytep)png_malloc(png_ptr,
+      png_ptr->quantize_index = (png_bytep)png_malloc(png_ptr,
          (png_uint_32)(num_palette * png_sizeof(png_byte)));
       for (i = 0; i < num_palette; i++)
-         png_ptr->dither_index[i] = (png_byte)i;
+         png_ptr->quantize_index[i] = (png_byte)i;
    }
 
    if (num_palette > maximum_colors)
@@ -192,12 +192,12 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
          int i;
 
          /* Initialize an array to sort colors */
-         png_ptr->dither_sort = (png_bytep)png_malloc(png_ptr,
+         png_ptr->quantize_sort = (png_bytep)png_malloc(png_ptr,
             (png_uint_32)(num_palette * png_sizeof(png_byte)));
 
-         /* Initialize the dither_sort array */
+         /* Initialize the quantize_sort array */
          for (i = 0; i < num_palette; i++)
-            png_ptr->dither_sort[i] = (png_byte)i;
+            png_ptr->quantize_sort[i] = (png_byte)i;
 
          /* Find the least used palette entries by starting a
           * bubble sort, and running it until we have sorted
@@ -214,14 +214,14 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
             done = 1;
             for (j = 0; j < i; j++)
             {
-               if (histogram[png_ptr->dither_sort[j]]
-                   < histogram[png_ptr->dither_sort[j + 1]])
+               if (histogram[png_ptr->quantize_sort[j]]
+                   < histogram[png_ptr->quantize_sort[j + 1]])
                {
                   png_byte t;
 
-                  t = png_ptr->dither_sort[j];
-                  png_ptr->dither_sort[j] = png_ptr->dither_sort[j + 1];
-                  png_ptr->dither_sort[j + 1] = t;
+                  t = png_ptr->quantize_sort[j];
+                  png_ptr->quantize_sort[j] = png_ptr->quantize_sort[j + 1];
+                  png_ptr->quantize_sort[j + 1] = t;
                   done = 0;
                }
             }
@@ -230,7 +230,7 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
          }
 
          /* Swap the palette around, and set up a table, if necessary */
-         if (full_dither)
+         if (full_quantize)
          {
             int j = num_palette;
 
@@ -239,11 +239,11 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
              */
             for (i = 0; i < maximum_colors; i++)
             {
-               if ((int)png_ptr->dither_sort[i] >= maximum_colors)
+               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
                {
                   do
                      j--;
-                  while ((int)png_ptr->dither_sort[j] >= maximum_colors);
+                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
                   palette[i] = palette[j];
                }
             }
@@ -258,32 +258,32 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
             for (i = 0; i < maximum_colors; i++)
             {
                /* Only move the colors we need to */
-               if ((int)png_ptr->dither_sort[i] >= maximum_colors)
+               if ((int)png_ptr->quantize_sort[i] >= maximum_colors)
                {
                   png_color tmp_color;
 
                   do
                      j--;
-                  while ((int)png_ptr->dither_sort[j] >= maximum_colors);
+                  while ((int)png_ptr->quantize_sort[j] >= maximum_colors);
 
                   tmp_color = palette[j];
                   palette[j] = palette[i];
                   palette[i] = tmp_color;
                   /* Indicate where the color went */
-                  png_ptr->dither_index[j] = (png_byte)i;
-                  png_ptr->dither_index[i] = (png_byte)j;
+                  png_ptr->quantize_index[j] = (png_byte)i;
+                  png_ptr->quantize_index[i] = (png_byte)j;
                }
             }
 
             /* Find closest color for those colors we are not using */
             for (i = 0; i < num_palette; i++)
             {
-               if ((int)png_ptr->dither_index[i] >= maximum_colors)
+               if ((int)png_ptr->quantize_index[i] >= maximum_colors)
                {
                   int min_d, k, min_k, d_index;
 
                   /* Find the closest color to one we threw out */
-                  d_index = png_ptr->dither_index[i];
+                  d_index = png_ptr->quantize_index[i];
                   min_d = PNG_COLOR_DIST(palette[d_index], palette[0]);
                   for (k = 1, min_k = 0; k < maximum_colors; k++)
                   {
@@ -298,12 +298,12 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
                      }
                   }
                   /* Point to closest color */
-                  png_ptr->dither_index[i] = (png_byte)min_k;
+                  png_ptr->quantize_index[i] = (png_byte)min_k;
                }
             }
          }
-         png_free(png_ptr, png_ptr->dither_sort);
-         png_ptr->dither_sort = NULL;
+         png_free(png_ptr, png_ptr->quantize_sort);
+         png_ptr->quantize_sort = NULL;
       }
       else
       {
@@ -410,19 +410,19 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
                         num_new_palette--;
                         palette[png_ptr->index_to_palette[j]]
                           = palette[num_new_palette];
-                        if (!full_dither)
+                        if (!full_quantize)
                         {
                            int k;
 
                            for (k = 0; k < num_palette; k++)
                            {
-                              if (png_ptr->dither_index[k] ==
+                              if (png_ptr->quantize_index[k] ==
                                  png_ptr->index_to_palette[j])
-                                 png_ptr->dither_index[k] =
+                                 png_ptr->quantize_index[k] =
                                     png_ptr->index_to_palette[next_j];
-                              if ((int)png_ptr->dither_index[k] ==
+                              if ((int)png_ptr->quantize_index[k] ==
                                  num_new_palette)
-                                 png_ptr->dither_index[k] =
+                                 png_ptr->quantize_index[k] =
                                     png_ptr->index_to_palette[j];
                            }
                         }
@@ -475,15 +475,15 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
    }
    png_ptr->num_palette = (png_uint_16)num_palette;
 
-   if (full_dither)
+   if (full_quantize)
    {
       int i;
       png_bytep distance;
-      int total_bits = PNG_DITHER_RED_BITS + PNG_DITHER_GREEN_BITS +
-         PNG_DITHER_BLUE_BITS;
-      int num_red = (1 << PNG_DITHER_RED_BITS);
-      int num_green = (1 << PNG_DITHER_GREEN_BITS);
-      int num_blue = (1 << PNG_DITHER_BLUE_BITS);
+      int total_bits = PNG_QUANTIZE_RED_BITS + PNG_QUANTIZE_GREEN_BITS +
+         PNG_QUANTIZE_BLUE_BITS;
+      int num_red = (1 << PNG_QUANTIZE_RED_BITS);
+      int num_green = (1 << PNG_QUANTIZE_GREEN_BITS);
+      int num_blue = (1 << PNG_QUANTIZE_BLUE_BITS);
       png_size_t num_entries = ((png_size_t)1 << total_bits);
 
       png_ptr->palette_lookup = (png_bytep )png_calloc(png_ptr,
@@ -496,16 +496,16 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
       for (i = 0; i < num_palette; i++)
       {
          int ir, ig, ib;
-         int r = (palette[i].red >> (8 - PNG_DITHER_RED_BITS));
-         int g = (palette[i].green >> (8 - PNG_DITHER_GREEN_BITS));
-         int b = (palette[i].blue >> (8 - PNG_DITHER_BLUE_BITS));
+         int r = (palette[i].red >> (8 - PNG_QUANTIZE_RED_BITS));
+         int g = (palette[i].green >> (8 - PNG_QUANTIZE_GREEN_BITS));
+         int b = (palette[i].blue >> (8 - PNG_QUANTIZE_BLUE_BITS));
 
          for (ir = 0; ir < num_red; ir++)
          {
             /* int dr = abs(ir - r); */
             int dr = ((ir > r) ? ir - r : r - ir);
-            int index_r = (ir << (PNG_DITHER_BLUE_BITS +
-                PNG_DITHER_GREEN_BITS));
+            int index_r = (ir << (PNG_QUANTIZE_BLUE_BITS +
+                PNG_QUANTIZE_GREEN_BITS));
 
             for (ig = 0; ig < num_green; ig++)
             {
@@ -513,7 +513,7 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
                int dg = ((ig > g) ? ig - g : g - ig);
                int dt = dr + dg;
                int dm = ((dr > dg) ? dr : dg);
-               int index_g = index_r | (ig << PNG_DITHER_BLUE_BITS);
+               int index_g = index_r | (ig << PNG_QUANTIZE_BLUE_BITS);
 
                for (ib = 0; ib < num_blue; ib++)
                {
@@ -536,7 +536,7 @@ png_set_dither(png_structp png_ptr, png_colorp palette,
       png_free(png_ptr, distance);
    }
 }
-#endif /* PNG_READ_DITHER_SUPPORTED */
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
 
 #if defined(PNG_READ_GAMMA_SUPPORTED) && defined(PNG_FLOATING_POINT_SUPPORTED)
 /* Transform the image from the file_gamma to the screen_gamma.  We
@@ -1229,8 +1229,8 @@ png_read_transform_info(png_structp png_ptr, png_infop info_ptr)
       info_ptr->color_type &= ~PNG_COLOR_MASK_COLOR;
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-   if (png_ptr->transformations & PNG_DITHER)
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   if (png_ptr->transformations & PNG_QUANTIZE)
    {
       if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||
           (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA)) &&
@@ -1451,13 +1451,13 @@ png_do_read_transformations(png_structp png_ptr)
       png_do_chop(&(png_ptr->row_info), png_ptr->row_buf + 1);
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
-   if (png_ptr->transformations & PNG_DITHER)
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+   if (png_ptr->transformations & PNG_QUANTIZE)
    {
-      png_do_dither((png_row_infop)&(png_ptr->row_info), png_ptr->row_buf + 1,
-         png_ptr->palette_lookup, png_ptr->dither_index);
+      png_do_quantize((png_row_infop)&(png_ptr->row_info), png_ptr->row_buf + 1,
+         png_ptr->palette_lookup, png_ptr->quantize_index);
       if (png_ptr->row_info.rowbytes == (png_uint_32)0)
-         png_error(png_ptr, "png_do_dither returned rowbytes=0");
+         png_error(png_ptr, "png_do_quantize returned rowbytes=0");
    }
 #endif
 
@@ -3790,16 +3790,16 @@ png_do_expand(png_row_infop row_info, png_bytep row,
 }
 #endif
 
-#ifdef PNG_READ_DITHER_SUPPORTED
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
 void /* PRIVATE */
-png_do_dither(png_row_infop row_info, png_bytep row,
-    png_bytep palette_lookup, png_bytep dither_lookup)
+png_do_quantize(png_row_infop row_info, png_bytep row,
+    png_bytep palette_lookup, png_bytep quantize_lookup)
 {
    png_bytep sp, dp;
    png_uint_32 i;
    png_uint_32 row_width=row_info->width;
 
-   png_debug(1, "in png_do_dither");
+   png_debug(1, "in png_do_quantize");
 
    {
       if (row_info->color_type == PNG_COLOR_TYPE_RGB &&
@@ -3821,14 +3821,14 @@ png_do_dither(png_row_infop row_info, png_bytep row,
              *    (((g >> 3) & 0x1f) << 5) |
              *    ((b >> 3) & 0x1f);
              */
-            p = (((r >> (8 - PNG_DITHER_RED_BITS)) &
-               ((1 << PNG_DITHER_RED_BITS) - 1)) <<
-               (PNG_DITHER_GREEN_BITS + PNG_DITHER_BLUE_BITS)) |
-               (((g >> (8 - PNG_DITHER_GREEN_BITS)) &
-               ((1 << PNG_DITHER_GREEN_BITS) - 1)) <<
-               (PNG_DITHER_BLUE_BITS)) |
-               ((b >> (8 - PNG_DITHER_BLUE_BITS)) &
-               ((1 << PNG_DITHER_BLUE_BITS) - 1));
+            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
+               ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
+               (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
+               (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
+               ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
+               (PNG_QUANTIZE_BLUE_BITS)) |
+               ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
+               ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
 
             *dp++ = palette_lookup[p];
          }
@@ -3850,14 +3850,14 @@ png_do_dither(png_row_infop row_info, png_bytep row,
             b = *sp++;
             sp++;
 
-            p = (((r >> (8 - PNG_DITHER_RED_BITS)) &
-               ((1 << PNG_DITHER_RED_BITS) - 1)) <<
-               (PNG_DITHER_GREEN_BITS + PNG_DITHER_BLUE_BITS)) |
-               (((g >> (8 - PNG_DITHER_GREEN_BITS)) &
-               ((1 << PNG_DITHER_GREEN_BITS) - 1)) <<
-               (PNG_DITHER_BLUE_BITS)) |
-               ((b >> (8 - PNG_DITHER_BLUE_BITS)) &
-               ((1 << PNG_DITHER_BLUE_BITS) - 1));
+            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
+               ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
+               (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
+               (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
+               ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
+               (PNG_QUANTIZE_BLUE_BITS)) |
+               ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
+               ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));
 
             *dp++ = palette_lookup[p];
          }
@@ -3867,12 +3867,12 @@ png_do_dither(png_row_infop row_info, png_bytep row,
          row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
       }
       else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
-         dither_lookup && row_info->bit_depth == 8)
+         quantize_lookup && row_info->bit_depth == 8)
       {
          sp = row;
          for (i = 0; i < row_width; i++, sp++)
          {
-            *sp = dither_lookup[*sp];
+            *sp = quantize_lookup[*sp];
          }
       }
    }