Revised comments about interpretation of the -quality value in coders/png.c

diff --git a/coders/png.c b/coders/png.c
index e191ed4ce729661880906bf51de6fd4968085e4c..6b1401e7400dbd58badc5a99f54a1d62c7c25cd1 100644 (file)
--- a/coders/png.c
+++ b/coders/png.c
@@ -10354,7 +10354,7 @@ static MagickBooleanType WriteOnePNGImage(MngInfo *mng_info,
 
      10's digit:
 
-        0: Use Z_HUFFMAN_ONLY strategy with the
+        0 or omitted: Use Z_HUFFMAN_ONLY strategy with the
            zlib default compression level
 
         1-9: the zlib compression level
@@ -10373,10 +10373,10 @@ static MagickBooleanType WriteOnePNGImage(MngInfo *mng_info,
              a MNG, othewise "none".  Did not work in IM-6.7.0-9
              and earlier because of a missing "else".
 
-        8:   Z_RLE strategy, all filters
+        8:   Z_RLE strategy (or Z_HUFFMAN_ONLY if quality < 10), all filters
              Unused prior to IM-6.7.0-10, was same as 6
 
-        9:   Z_RLE strategy, no PNG filters
+        9:   Z_RLE strategy (or Z_HUFFMAN_ONLY if quality < 10), no PNG filters
              Unused prior to IM-6.7.0-10, was same as 6
 
     Note that using the -quality option, not all combinations of