[libpng16] Added PNG_IMAGE_FLAG_FAST for the benefit of applications that

store intermediate files, or intermediate in-memory data, while processing
image data with the simplified API.  The option makes the files larger
but faster to write and read.  pngstest now uses this by default; this
can be disabled with the --slow option.

ANNOUNCE

@@ -1,5 +1,5 @@
 
-Libpng 1.6.0beta15 - February 29, 2012
+Libpng 1.6.0beta15 - March 2, 2012
 
 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.
@@ -234,12 +234,17 @@ Version 1.6.0beta14 [February 27, 2012]
   Added information about the new limits in the manual.
   Updated Makefile.in
 
-Version 1.6.0beta15 [February 29, 2012]
+Version 1.6.0beta15 [March 2, 2012]
   Removed unused "current_text" members of png_struct and the png_free()
     of png_ptr->current_text from pngread.c
   Rewrote pngstest.c for substantial speed improvement.
   Fixed transparent pixel and 16-bit rgb tests in pngstest and removed a
     spurious check in pngwrite.c
+  Added PNG_IMAGE_FLAG_FAST for the benefit of applications that store
+    intermediate files, or intermediate in-memory data, while processing
+    image data with the simplified API.  The option makes the files larger
+    but faster to write and read.  pngstest now uses this by default; this
+    can be disabled with the --slow option.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

CHANGES

@@ -3986,12 +3986,17 @@ Version 1.6.0beta14 [February 27, 2012]
   Added information about the new limits in the manual.
   Updated Makefile.in
 
-Version 1.6.0beta15 [February 29, 2012]
+Version 1.6.0beta15 [March 2, 2012]
   Removed unused "current_text" members of png_struct and the png_free()
     of png_ptr->current_text from pngread.c
   Rewrote pngstest.c for substantial speed improvement.
   Fixed transparent pixel and 16-bit rgb tests in pngstest and removed a
     spurious check in pngwrite.c
+  Added PNG_IMAGE_FLAG_FAST for the benefit of applications that store
+    intermediate files, or intermediate in-memory data, while processing
+    image data with the simplified API.  The option makes the files larger
+    but faster to write and read.  pngstest now uses this by default; this
+    can be disabled with the --slow option.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

contrib/libtests/pngstest.c

@@ -304,6 +304,7 @@ compare_16bit(int v1, int v2, int error_limit, int multiple_algorithms)
 #define KEEP_TMPFILES 16 /* else delete temporary files */
 #define KEEP_GOING 32
 #define ACCUMULATE 64
+#define FAST_WRITE 128
 
 static void
 print_opts(png_uint_32 opts)
@@ -1932,7 +1933,7 @@ static png_uint_16 gpc_error[16/*in*/][16/*out*/][4/*a*/] =
   { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
   { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
  }, { /* input: sRGB-rgb */
-  { 0, 0, 17, 0 }, { 0, 0, 17, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
+  { 0, 0, 19, 0 }, { 0, 0, 19, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
   { 0, 0, 863, 0 }, { 0, 0, 863, 0 }, { 0, 0, 811, 0 }, { 0, 0, 811, 0 },
   { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
   { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
@@ -2010,7 +2011,7 @@ static png_uint_16 gpc_error_via_linear[16][4/*out*/][4] =
  }, { /* input: sRGB-gray+alpha */
   { 0, 6, 3, 0 }, { 0, 53, 3, 0 }, { 0, 6, 3, 0 }, { 0, 53, 3, 0 }
  }, { /* input: sRGB-rgb */
-  { 0, 0, 17, 0 }, { 0, 0, 17, 0 }, { 0, 0, 14, 0 }, { 0, 0, 14, 0 }
+  { 0, 0, 19, 0 }, { 0, 0, 19, 0 }, { 0, 0, 15, 0 }, { 0, 0, 15, 0 }
  }, { /* input: sRGB-rgb+alpha */
   { 0, 8, 10, 0 }, { 0, 13, 10, 0 }, { 0, 12, 8, 0 }, { 0, 53, 8, 0 }
  }, { /* input: linear-gray */
@@ -3083,6 +3084,9 @@ read_one_file(Image *image)
 static int
 write_one_file(Image *output, Image *image, int convert_to_8bit)
 {
+   if (image->opts & FAST_WRITE)
+      image->image.flags |= PNG_IMAGE_FLAG_FAST;
+
    if (image->opts & USE_STDIO)
    {
       FILE *f = tmpfile();
@@ -3303,7 +3307,7 @@ testimage(Image *image, png_uint_32 opts, format_list *pf)
 int
 main(int argc, char **argv)
 {
-   png_uint_32 opts = 0;
+   png_uint_32 opts = FAST_WRITE;
    format_list formats;
    const char *touch = NULL;
    int log_pass = 0;
@@ -3347,6 +3351,10 @@ main(int argc, char **argv)
          opts &= ~KEEP_TMPFILES;
       else if (strcmp(arg, "--keep-going") == 0)
          opts |= KEEP_GOING;
+      else if (strcmp(arg, "--fast") == 0)
+         opts |= FAST_WRITE;
+      else if (strcmp(arg, "--slow") == 0)
+         opts &= ~FAST_WRITE;
       else if (strcmp(arg, "--accumulate") == 0)
          opts |= ACCUMULATE;
       else if (strcmp(arg, "--redundant") == 0)

png.h

@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.6.0beta15 - February 27, 2012
+ * libpng version 1.6.0beta15 - March 2, 2012
  * Copyright (c) 1998-2012 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 1.6.0beta15 - February 27, 2012: Glenn
+ *   libpng versions 0.97, January 1998, through 1.6.0beta15 - March 2, 2012: Glenn
  *   See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -198,7 +198,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.6.0beta15, February 27, 2012, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.6.0beta15, March 2, 2012, are
  * Copyright (c) 2004, 2006-2012 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:
@@ -310,7 +310,7 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    February 27, 2012
+ *    March 2, 2012
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
@@ -376,7 +376,7 @@
 /* Version information for png.h - this should match the version in png.c */
 #define PNG_LIBPNG_VER_STRING "1.6.0beta15"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.6.0beta15 - February 27, 2012\n"
+     " libpng version 1.6.0beta15 - March 2, 2012\n"
 
 #define PNG_LIBPNG_VER_SONUM   16
 #define PNG_LIBPNG_VER_DLLNUM  16
@@ -2943,6 +2943,17 @@ typedef struct
     * correspond to the red, green and blue end-points defined by sRGB.
     */
 
+#define PNG_IMAGE_FLAG_FAST 0x02
+   /* On write emphasise speed over compression; the resultant PNG file will be
+    * larger but will be produced significantly faster, particular for large
+    * images.  Do not use this option for images which will be distributed, only
+    * used it when producing intermediate files that will be read back in
+    * repeatedly.  For a typical 24-bit image the option will double the read
+    * speed at the cost of increasing the image size by 25%, however for many
+    * more compressible images the PNG file can be 10 times larger with only a
+    * slight speed gain.
+    */
+
 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
 /* READ APIs
  * ---------

pngwrite.c

@@ -731,6 +731,15 @@ png_write_row(png_structrp png_ptr, png_const_bytep row)
    }
 #endif
 
+#if 0 /* To do: implement png_do_check_palette_indexes() */
+   /* Check for out-of-range palette index */
+   if (png_ptr->num_palette < (1 << png_ptr->bit_depth))
+      png_do_check_palette_indexes(&row_info, png_ptr->row_buf + 1,
+        png_ptr->num_palette_max);
+   if (png_ptr->num_palette_max > num_palette + 1)
+      png_warning(png_ptr, "Palette index exceeded num_palette");
+#endif
+
    /* Find a filter if necessary, filter the row and write it out. */
    png_write_find_filter(png_ptr, &row_info);
 
@@ -2109,6 +2118,18 @@ png_image_write_main(png_voidp argument)
       display->row_bytes = row_bytes;
    }
 
+   /* Apply 'fast' options if the flag is set. */
+   if ((image->flags & PNG_IMAGE_FLAG_FAST) != 0)
+   {
+      png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, PNG_NO_FILTERS);
+      /* NOTE: determined by experiment using pngstest, this reflects some
+       * balance between the time to write the image once and the time to read
+       * it about 50 times.  The speed-up in pngstest was about 10-20% of the
+       * total (user) time on a heavily loaded system.
+       */
+      png_set_compression_level(png_ptr, 3);
+   }
+
    /* Check for the cases that currently require a pre-transform on the row
     * before it is written.  This only applies when the input is 16-bit and
     * either there is an alpha channel or it is converted to 8-bit.