Imported from libpng-1.0.1e.tar
diff --git a/pngwutil.c b/pngwutil.c
index 8e0dc21..969386e 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -1,12 +1,11 @@
/* pngwutil.c - utilities to write a PNG file
*
- * 1.0.1d
+ * libpng 1.0.1e - June 6, 1998
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
- * May 21, 1998
*/
#define PNG_INTERNAL
@@ -575,7 +574,8 @@
}
#endif
-#if defined(PNG_WRITE_tEXt_SUPPORTED) || defined(PNG_WRITE_zTXt_SUPPORTED)
+#if defined(PNG_WRITE_tEXt_SUPPORTED) || defined(PNG_WRITE_zTXt_SUPPORTED) || \
+ defined(PNG_WRITE_pCAL_SUPPORTED)
/* Check that the tEXt or zTXt keyword is valid per PNG 1.0 specification,
* and if invalid, correct the keyword rather than discarding the entire
* chunk. The PNG 1.0 specification requires keywords 1-79 characters in
@@ -1416,10 +1416,19 @@
* as the "minimum sum of absolute differences" heuristic. Other
* heuristics are the "weighted minimum sum of absolute differences"
* (experimental and can in theory improve compression), and the "zlib
- * predictive" method (not implemented in libpng 0.95), which does test
- * compressions of lines using different filter methods, and then chooses
- * the (series of) filter(s) which give minimum compressed data size (VERY
+ * predictive" method (not implemented yet), which does test compressions
+ * of lines using different filter methods, and then chooses the
+ * (series of) filter(s) that give minimum compressed data size (VERY
* computationally expensive).
+ *
+ * GRR 980525: consider also
+ * (1) minimum sum of absolute differences from running average (i.e.,
+ * keep running sum of non-absolute differences & count of bytes)
+ * [track dispersion, too? restart average if dispersion too large?]
+ * (1b) minimum sum of absolute differences from sliding average, probably
+ * with window size <= deflate window (usually 32K)
+ * (2) minimum sum of squared differences from zero or running average
+ * (i.e., ~ root-mean-square approach)
*/