Handle empty DecodeParams array for (fixes #331)

On read, ignore /DecodeParms when empty list; on write, delete it.
Some files have been found that include an empty list for
/DecodeParms, but this is not technically compliant with the spec, and
the only sensible interpretation is to treat it as if there are no
decode parameters.

1 files changed, 8 insertions, 0 deletions

diff --git a/libqpdf/QPDFWriter.cc b/libqpdf/QPDFWriter.cc
index fee287bc..0cc0547d 100644
--- a/libqpdf/QPDFWriter.cc
+++ b/libqpdf/QPDFWriter.cc
@@ -1604,6 +1604,14 @@ QPDFWriter::unparseObject(QPDFObjectHandle object, int level,
             // Suppress /Length since we will write it manually
             object.removeKey("/Length");
 
+            // If /DecodeParms is an empty list, remove it.
+            if (object.getKey("/DecodeParms").isArray() &&
+                (0 == object.getKey("/DecodeParms").getArrayNItems()))
+            {
+                QTC::TC("qpdf", "QPDFWriter remove empty DecodeParms");
+                object.removeKey("/DecodeParms");
+            }
+
 	    if (flags & f_filtered)
             {
                 // We will supply our own filter and decode