[libpng16] Improved pngstest fine tuning of error numbers, new test file

generator.  The generator generates images that test the full range of sample
values, allow the error numbers in pngstest to be tuned and checked.  makepng
also allows generation of images with extra chunks, although this is
still work-in-progress.

ANNOUNCE

@@ -245,6 +245,11 @@ Version 1.6.0beta15 [March 2, 2012]
     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.
+  Improved pngstest fine tuning of error numbers, new test file generator.
+    The generator generates images that test the full range of sample values,
+    allow the error numbers in pngstest to be tuned and checked.  makepng
+    also allows generation of images with extra chunks, although this is
+    still work-in-progress.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

CHANGES

@@ -3997,6 +3997,11 @@ Version 1.6.0beta15 [March 2, 2012]
     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.
+  Improved pngstest fine tuning of error numbers, new test file generator.
+    The generator generates images that test the full range of sample values,
+    allow the error numbers in pngstest to be tuned and checked.  makepng
+    also allows generation of images with extra chunks, although this is
+    still work-in-progress.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

contrib/libtests/gentests.sh

+#!/bin/sh
+#
+# Copyright (c) 2012 John Cunningham Bowler
+#
+# Last changed in libpng 1.6.0 [(PENDING RELEASE)]
+#
+# This code is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer
+# and license in png.h
+#
+# Generate a set of PNG test images.  The images are generated in a
+# sub-directory called 'tests' by default, however a command line argument will
+# change that name.  The generation requires a built version of makepng in the
+# current directory.
+#
+usage(){
+   exec >&2
+   echo "$0 [<directory>]"
+   echo '  Generate a set of PNG test files in "directory" ("tests" by default)'
+   exit 1
+}
+
+mp="$PWD/makepng"
+test -x "$mp" || {
+   exec >&2
+   echo "$0: the 'makepng' program must exist"
+   echo "  in the directory within which this program:"
+   echo "    $mp"
+   echo "  is executed"
+   usage
+}
+
+# Just one argument: the directory
+testdir="tests"
+test $# -gt 1 && {
+   testdir="$1"
+   shift
+}
+test $# -eq 0 || usage
+
+# Take care not to clobber something
+if test -e "$testdir"
+then
+   test -d "$testdir" || usage
+else
+   # mkdir -p isn't portable, so do the following
+   mkdir "$testdir" 2>/dev/null || mkdir -p "$testdir" || usage
+fi
+
+# This fails in a very satisfactory way if it's not accessible
+cd "$testdir"
+:>"test$$.png" || {
+   exec >&2
+   echo "$testdir: directory not writable"
+   usage
+}
+rm "test$$.png" || {
+   exec >&2
+   echo "$testdir: you have create but not write privileges here."
+   echo "  This is unexpected.  You have a spurion; "'"'"test$$.png"'"'"."
+   echo "  You need to remove this yourself.  Try a different directory."
+   exit 1
+}
+
+# Now call makepng ($mp) to create every file we can think of with a
+# reasonable name
+doit(){
+   for gamma in "" --sRGB --linear --1.8
+   do
+      case "$gamma" in
+         "")
+            gname=;;
+         --sRGB)
+            gname="-srgb";;
+         --linear)
+            gname="-lin";;
+         --1.8)
+            gname="-18";;
+         *)
+            gname="-$gamma";;
+      esac
+      "$mp" $gamma "$1" "$2" "test-$1-$2$gname.png"
+   done
+}
+#
+for ct in gray palette
+do
+   for bd in 1 2 4 8
+   do
+      doit "$ct" "$bd"
+   done
+done
+#
+doit "gray" "16"
+#
+for ct in gray-alpha rgb rgb-alpha
+do
+   for bd in 8 16
+   do
+      doit "$ct" "$bd"
+   done
+done

contrib/libtests/pngstest.c

@@ -1924,41 +1924,41 @@ static png_uint_16 gpc_error[16/*in*/][16/*out*/][4/*a*/] =
 {
  { /* input: sRGB-gray */
   { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
-  { 0, 0, 261, 0 }, { 0, 0, 261, 0 }, { 0, 0, 261, 0 }, { 0, 0, 261, 0 },
+  { 0, 0, 372, 0 }, { 0, 0, 372, 0 }, { 0, 0, 372, 0 }, { 0, 0, 372, 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 }
  }, { /* input: sRGB-gray+alpha */
-  { 0, 13, 0, 0 }, { 0, 0, 0, 0 }, { 0, 16, 0, 0 }, { 0, 0, 0, 0 },
-  { 0, 678, 710, 0 }, { 0, 678, 710, 0 }, { 0, 678, 710, 0 }, { 0, 678, 710, 0 },
+  { 0, 18, 0, 0 }, { 0, 0, 0, 0 }, { 0, 20, 0, 0 }, { 0, 0, 0, 0 },
+  { 0, 897, 788, 0 }, { 0, 897, 788, 0 }, { 0, 897, 788, 0 }, { 0, 897, 788, 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 }
  }, { /* input: sRGB-rgb */
   { 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, 893, 0 }, { 0, 0, 893, 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 }
  }, { /* input: sRGB-rgb+alpha */
-  { 0, 3, 7, 0 }, { 0, 3, 7, 0 }, { 0, 13, 0, 0 }, { 0, 0, 0, 0 },
-  { 0, 688, 743, 0 }, { 0, 688, 743, 0 }, { 0, 688, 743, 0 }, { 0, 688, 743, 0 },
+  { 0, 4, 7, 0 }, { 0, 14, 7, 0 }, { 0, 19, 0, 0 }, { 0, 0, 0, 0 },
+  { 0, 832, 764, 0 }, { 0, 832, 764, 0 }, { 0, 897, 788, 0 }, { 0, 897, 788, 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 }
  }, { /* input: linear-gray */
-  { 0, 0, 6, 0 }, { 0, 0, 6, 0 }, { 0, 0, 6, 0 }, { 0, 0, 6, 0 },
+  { 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 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 },
   { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
  }, { /* input: linear-gray+alpha */
-  { 0, 62, 6, 0 }, { 0, 2, 6, 0 }, { 0, 66, 6, 0 }, { 0, 2, 6, 0 },
+  { 0, 74, 9, 0 }, { 0, 20, 9, 0 }, { 0, 74, 9, 0 }, { 0, 20, 9, 0 },
   { 0, 0, 0, 0 }, { 0, 1, 0, 0 }, { 0, 0, 0, 0 }, { 0, 1, 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, 0 }
  }, { /* input: linear-rgb */
-  { 0, 0, 2, 0 }, { 0, 0, 2, 0 }, { 0, 0, 3, 0 }, { 0, 0, 3, 0 },
+  { 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 },
   { 0, 0, 4, 0 }, { 0, 0, 4, 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 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
  }, { /* input: linear-rgb+alpha */
-  { 0, 124, 143, 0 }, { 0, 2, 7, 0 }, { 0, 66, 7, 0 }, { 0, 3, 7, 0 },
+  { 0, 126, 143, 0 }, { 0, 9, 7, 0 }, { 0, 74, 9, 0 }, { 0, 16, 9, 0 },
   { 0, 4, 4, 0 }, { 0, 5, 4, 0 }, { 0, 0, 0, 0 }, { 0, 1, 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, 0 }
@@ -1978,10 +1978,10 @@ static png_uint_16 gpc_error[16/*in*/][16/*out*/][4/*a*/] =
   { 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
   { 0, 0, 460, 0 }, { 0, 0, 460, 0 }, { 0, 0, 263, 0 }, { 0, 0, 263, 0 }
  }, { /* input: color-mapped-sRGB-rgb+alpha */
-  { 0, 0, 8, 0 }, { 0, 0, 8, 0 }, { 0, 0, 8, 0 }, { 0, 0, 8, 0 },
-  { 0, 0, 427, 0 }, { 0, 0, 427, 0 }, { 0, 0, 263, 0 }, { 0, 0, 263, 0 },
-  { 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
-  { 0, 0, 460, 0 }, { 0, 0, 460, 0 }, { 0, 0, 263, 0 }, { 0, 0, 263, 0 }
+  { 0, 6, 8, 0 }, { 0, 7, 8, 0 }, { 0, 75, 8, 0 }, { 0, 9, 8, 0 },
+  { 0, 585, 427, 0 }, { 0, 585, 427, 0 }, { 0, 717, 409, 0 }, { 0, 717, 409, 0 },
+  { 0, 1, 1, 0 }, { 0, 1, 1, 0 }, { 0, 1, 0, 0 }, { 0, 0, 0, 0 },
+  { 0, 13323, 460, 0 }, { 0, 334, 460, 0 }, { 0, 16480, 263, 0 }, { 0, 243, 263, 0 }
  }, { /* input: color-mapped-linear-gray */
   { 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 },
@@ -1991,17 +1991,17 @@ 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 },
   { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 },
-  { 0, 0, 0, 0 }, { 0, 0, 282, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
+  { 0, 0, 0, 0 }, { 0, 253, 282, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
  }, { /* input: color-mapped-linear-rgb */
   { 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, 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, 263, 0 }, { 0, 0, 0, 0 }
+  { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 265, 0 }, { 0, 0, 0, 0 }
  }, { /* input: color-mapped-linear-rgb+alpha */
   { 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, 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, 263, 0 }
+  { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 243, 265, 0 }
  }
 };
 static png_uint_16 gpc_error_via_linear[16][4/*out*/][4] =
@@ -2009,19 +2009,19 @@ static png_uint_16 gpc_error_via_linear[16][4/*out*/][4] =
  { /* input: sRGB-gray */
   { 0, 0, 7, 0 }, { 0, 0, 7, 0 }, { 0, 0, 7, 0 }, { 0, 0, 7, 0 }
  }, { /* input: sRGB-gray+alpha */
-  { 0, 6, 3, 0 }, { 0, 53, 3, 0 }, { 0, 6, 3, 0 }, { 0, 53, 3, 0 }
+  { 0, 15, 15, 0 }, { 0, 186, 15, 0 }, { 0, 15, 15, 0 }, { 0, 186, 15, 0 }
  }, { /* input: sRGB-rgb */
   { 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 }
+  { 0, 9, 10, 0 }, { 0, 180, 10, 0 }, { 0, 14, 15, 0 }, { 0, 186, 15, 0 }
  }, { /* input: linear-gray */
   { 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 1, 0 }
  }, { /* input: linear-gray+alpha */
-  { 0, 1, 1, 0 }, { 0, 0, 1, 0 }, { 0, 1, 1, 0 }, { 0, 0, 1, 0 }
+  { 0, 1, 1, 0 }, { 0, 1, 1, 0 }, { 0, 1, 1, 0 }, { 0, 1, 1, 0 }
  }, { /* input: linear-rgb */
-  { 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
+  { 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 1, 0 }, { 0, 0, 1, 0 }
  }, { /* input: linear-rgb+alpha */
-  { 0, 1, 1, 0 }, { 0, 1, 1, 0 }, { 0, 1, 1, 0 }, { 0, 0, 1, 0 }
+  { 0, 1, 1, 0 }, { 0, 8, 1, 0 }, { 0, 1, 1, 0 }, { 0, 1, 1, 0 }
  }, { /* input: color-mapped-sRGB-gray */
   { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
  }, { /* input: color-mapped-sRGB-gray+alpha */
@@ -2029,7 +2029,7 @@ static png_uint_16 gpc_error_via_linear[16][4/*out*/][4] =
  }, { /* input: color-mapped-sRGB-rgb */
   { 0, 0, 12, 0 }, { 0, 0, 12, 0 }, { 0, 0, 1, 0 }, { 0, 0, 1, 0 }
  }, { /* input: color-mapped-sRGB-rgb+alpha */
-  { 0, 0, 8, 0 }, { 0, 0, 8, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
+  { 0, 4, 8, 0 }, { 0, 9, 8, 0 }, { 0, 8, 3, 0 }, { 0, 32, 3, 0 }
  }, { /* input: color-mapped-linear-gray */
   { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }
  }, { /* input: color-mapped-linear-gray+alpha */
@@ -2043,29 +2043,29 @@ static png_uint_16 gpc_error_via_linear[16][4/*out*/][4] =
 static png_uint_16 gpc_error_to_colormap[8/*i*/][8/*o*/][4] =
 {
  { /* input: sRGB-gray */
-  { 0, 0, 8, 0 }, { 0, 0, 8, 0 }, { 0, 0, 8, 0 }, { 0, 0, 8, 0 },
-  { 0, 0, 559, 0 }, { 0, 0, 559, 0 }, { 0, 0, 559, 0 }, { 0, 0, 559, 0 }
+  { 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 }, { 0, 0, 9, 0 },
+  { 0, 0, 560, 0 }, { 0, 0, 560, 0 }, { 0, 0, 560, 0 }, { 0, 0, 560, 0 }
  }, { /* input: sRGB-gray+alpha */
-  { 0, 10, 2, 0 }, { 0, 255, 2, 25 }, { 0, 88, 2, 0 }, { 0, 255, 2, 25 },
-  { 0, 824, 745, 0 }, { 0, 15462, 745, 6425 }, { 0, 824, 745, 0 }, { 0, 15462, 745, 6425 }
+  { 0, 19, 2, 0 }, { 0, 255, 2, 25 }, { 0, 88, 2, 0 }, { 0, 255, 2, 25 },
+  { 0, 1012, 745, 0 }, { 0, 16026, 745, 6425 }, { 0, 1012, 745, 0 }, { 0, 16026, 745, 6425 }
  }, { /* input: sRGB-rgb */
-  { 0, 0, 17, 0 }, { 0, 0, 17, 0 }, { 0, 0, 25, 0 }, { 0, 0, 25, 0 },
-  { 0, 0, 871, 0 }, { 0, 0, 871, 0 }, { 0, 0, 13677, 0 }, { 0, 0, 13677, 0 }
+  { 0, 0, 19, 0 }, { 0, 0, 19, 0 }, { 0, 0, 25, 0 }, { 0, 0, 25, 0 },
+  { 0, 0, 937, 0 }, { 0, 0, 937, 0 }, { 0, 0, 13677, 0 }, { 0, 0, 13677, 0 }
  }, { /* input: sRGB-rgb+alpha */
-  { 0, 63, 77, 0 }, { 0, 162, 7, 25 }, { 0, 220, 25, 0 }, { 0, 255, 25, 63 },
-  { 0, 17534, 18452, 0 }, { 0, 15614, 1001, 6425 }, { 0, 13050, 13677, 0 }, { 0, 48573, 13677, 16191 }
+  { 0, 63, 77, 0 }, { 0, 255, 19, 25 }, { 0, 220, 25, 0 }, { 0, 255, 25, 67 },
+  { 0, 17534, 18491, 0 }, { 0, 15614, 2824, 6425 }, { 0, 14019, 13677, 0 }, { 0, 48573, 13677, 17219 }
  }, { /* input: linear-gray */
-  { 0, 0, 6, 0 }, { 0, 0, 6, 0 }, { 0, 0, 6, 0 }, { 0, 0, 6, 0 },
-  { 0, 0, 761, 0 }, { 0, 0, 761, 0 }, { 0, 0, 761, 0 }, { 0, 0, 761, 0 }
+  { 0, 0, 73, 0 }, { 0, 0, 73, 0 }, { 0, 0, 73, 0 }, { 0, 0, 73, 0 },
+  { 0, 0, 18817, 0 }, { 0, 0, 18817, 0 }, { 0, 0, 18817, 0 }, { 0, 0, 18817, 0 }
  }, { /* input: linear-gray+alpha */
-  { 0, 58, 6, 0 }, { 0, 255, 6, 25 }, { 0, 91, 6, 0 }, { 0, 255, 6, 25 },
-  { 0, 585, 783, 0 }, { 0, 12262, 783, 6342 }, { 0, 585, 783, 0 }, { 0, 12262, 783, 6342 }
+  { 0, 74, 74, 0 }, { 0, 255, 74, 25 }, { 0, 97, 74, 0 }, { 0, 255, 74, 25 },
+  { 0, 18919, 18907, 0 }, { 0, 24549, 18907, 6552 }, { 0, 18919, 18907, 0 }, { 0, 24549, 18907, 6552 }
  }, { /* input: linear-rgb */
-  { 0, 0, 2, 0 }, { 0, 0, 2, 0 }, { 0, 0, 26, 0 }, { 0, 0, 26, 0 },
-  { 0, 0, 766, 0 }, { 0, 0, 766, 0 }, { 0, 0, 12684, 0 }, { 0, 0, 12684, 0 }
+  { 0, 0, 73, 0 }, { 0, 0, 73, 0 }, { 0, 0, 98, 0 }, { 0, 0, 98, 0 },
+  { 0, 0, 18664, 0 }, { 0, 0, 18664, 0 }, { 0, 0, 24998, 0 }, { 0, 0, 24998, 0 }
  }, { /* input: linear-rgb+alpha */
-  { 0, 181, 196, 0 }, { 0, 179, 7, 25 }, { 206, 186, 29, 0 }, { 0, 255, 29, 62 },
-  { 0, 17173, 18137, 0 }, { 0, 14770, 1178, 6342 }, { 0, 11165, 13107, 0 }, { 0, 46509, 13107, 15983 }
+  { 0, 181, 196, 0 }, { 0, 255, 61, 25 }, { 206, 187, 98, 0 }, { 0, 255, 98, 67 },
+  { 0, 18141, 18137, 0 }, { 0, 17494, 17504, 6553 }, { 0, 24979, 24992, 0 }, { 0, 46509, 24992, 17347 }
  }
 };
 /* END MACHINE GENERATED */
@@ -2488,11 +2488,16 @@ cmppixel(Transform *transform, png_const_voidp in, png_const_voidp out,
 
    transform->out_gp(&pixel_out, out);
 
-   /* Eliminate the case where both the input and output pixel are transparent
-    * and the output is 8-bit - any component values are valid.
+   /* Eliminate the case where the input and output values match exactly. */
+   if (pixel_calc.a == pixel_out.a && pixel_calc.r == pixel_out.r &&
+      pixel_calc.g == pixel_out.g && pixel_calc.b == pixel_out.b)
+      return 1;
+
+   /* Eliminate the case where the output pixel is transparent and the output
+    * is 8-bit - any component values are valid.  Don't check the input alpha
+    * here to also skip the 16-bit small alpha cases.
     */
-   if (transform->output_8bit &&
-      pixel_in.a == 0 && pixel_calc.a == 0 && pixel_out.a == 0)
+   if (transform->output_8bit && pixel_calc.a == 0 && pixel_out.a == 0)
       return 1;
 
    /* Check for alpha errors first; an alpha error can damage the components too
@@ -2513,6 +2518,13 @@ cmppixel(Transform *transform, png_const_voidp in, png_const_voidp out,
       }
    }
 
+   /* Now if *either* of the output alphas are 0 but alpha is within tolerance
+    * eliminate the 8-bit component comparison.
+    */
+   if (errmsg == NULL && transform->output_8bit &&
+      (pixel_calc.a == 0 || pixel_out.a == 0))
+      return 1;
+
    if (errmsg == NULL) /* else just signal an alpha error */
    {
       int err_r = abs(pixel_calc.r - pixel_out.r);
@@ -2722,22 +2734,35 @@ compare_two_images(Image *a, Image *b, int via_linear,
          for (y=0; y<256; ++y, a_cmap += a_sample, b_cmap += b_sample)
             if (in_use[y])
          {
+            /* The colormap entries should be valid, but because libpng doesn't
+             * do any checking at present the original image may contain invalid
+             * pixel values.  These cause an error here (at present) unless
+             * accumulating errors in which case the program just ignores them.
+             */
             if (y >= a->image.colormap_entries)
+            {
+               if ((a->opts & ACCUMULATE) == 0)
                {
-               char pindex[4];
-               sprintf(pindex, "%lu", (unsigned long)y);
-               return logerror(a, a->file_name, "bad pixel index ", pindex);
+                  char pindex[4];
+                  sprintf(pindex, "%lu", (unsigned long)y);
+                  logerror(a, a->file_name, ": bad pixel index: ", pindex);
                }
+               result = 0;
+            }
 
-            if (y >= b->image.colormap_entries)
-               {
-               char pindex[4];
-               sprintf(pindex, "%lu", (unsigned long)y);
-               return logerror(b, b->file_name, "bad pixel index ", pindex);
-               }
+            else if (y >= b->image.colormap_entries)
+            {
+               if ((a->opts & ACCUMULATE) == 0)
+                  {
+                  char pindex[4];
+                  sprintf(pindex, "%lu", (unsigned long)y);
+                  logerror(b, b->file_name, ": bad pixel index: ", pindex);
+                  }
+               result = 0;
+            }
 
             /* All the mismatches are logged here; there can only be 256! */
-            if (!cmppixel(&tr, a_cmap, b_cmap, 0, y))
+            else if (!cmppixel(&tr, a_cmap, b_cmap, 0, y))
                result = 0;
          }
 
@@ -2748,6 +2773,7 @@ compare_two_images(Image *a, Image *b, int via_linear,
             tr.error_ptr[1] = tr.error[1];
             tr.error_ptr[2] = tr.error[2];
             tr.error_ptr[3] = tr.error[3];
+            result = 1; /* force a continue */
          }
 
          return result;
@@ -3304,6 +3330,38 @@ testimage(Image *image, png_uint_32 opts, format_list *pf)
    return result;
 }
 
+static int
+test_one_file(const char *file_name, format_list *formats, png_uint_32 opts,
+   int stride_extra, int log_pass)
+{
+   int result;
+   Image image;
+
+   newimage(&image);
+   initimage(&image, opts, file_name, stride_extra);
+   result = read_one_file(&image);
+   if (result)
+      result = testimage(&image, opts, formats);
+   freeimage(&image);
+
+   if (log_pass)
+   {
+      if (result)
+         printf("PASS:");
+
+      else
+         printf("FAIL:");
+
+      print_opts(opts);
+      printf(" %s\n", file_name);
+   }
+
+   else if (!result)
+      exit(1);
+
+   return result;
+}
+
 int
 main(int argc, char **argv)
 {
@@ -3383,7 +3441,7 @@ main(int argc, char **argv)
 
          format_set(&formats, format);
       }
-      else if (arg[0] == '-')
+      else if (arg[0] == '-' && arg[1] != 0 && (arg[1] != '0' || arg[2] != 0))
       {
          fflush(stdout);
          fprintf(stderr, "%s: unknown option: %s\n", argv[0], arg);
@@ -3391,36 +3449,57 @@ main(int argc, char **argv)
       }
       else
       {
-         int result;
-         Image image;
-
          if (format_is_initial(&formats))
             format_default(&formats, redundant);
 
-         newimage(&image);
-         initimage(&image, opts, arg, stride_extra);
-         result = read_one_file(&image);
-         if (result)
-            result = testimage(&image, opts, &formats);
-         freeimage(&image);
-
-         if (log_pass)
+         if (arg[0] == '-')
          {
-            if (result)
-               printf("PASS:");
+            const int term = (arg[1] == '0' ? 0 : '\n');
+            unsigned int ich = 0;
 
-            else
+            /* Loop reading files, use a static buffer to simplify this and just
+             * stop if the name gets to long.
+             */
+            static char buffer[4096];
+
+            do
             {
-               printf("FAIL:");
-               retval = 1;
-            }
+               int ch = getchar();
+
+               /* Don't allow '\0' in file names, and terminate with '\n' or,
+                * for -0, just '\0' (use -print0 to find to make this work!)
+                */
+               if (ch == EOF || ch == term || ch == 0)
+               {
+                  buffer[ich] = 0;
 
-            print_opts(opts);
-            printf(" %s\n", arg);
+                  if (ich > 0 && !test_one_file(buffer, &formats, opts,
+                     stride_extra, log_pass))
+                     retval = 1;
+
+                  if (ch == EOF)
+                     break;
+
+                  ich = 0;
+                  --ich; /* so that the increment below sets it to 0 again */
+               }
+
+               else
+                  buffer[ich] = (char)ch;
+            } while (++ich < sizeof buffer);
+
+            if (ich)
+            {
+               buffer[32] = 0;
+               buffer[4095] = 0;
+               fprintf(stderr, "%s...%s: file name too long\n", buffer,
+                  buffer+(4096-32));
+               exit(1);
+            }
          }
 
-         else if (!result)
-            exit(1);
+         else if (!test_one_file(arg, &formats, opts, stride_extra, log_pass))
+            retval = 1;
       }
    }