handle stream filter abbreviations from table H.1

git-svn-id: svn+q:///qpdf/trunk@1025 71b93d88-0707-0410-a8cf-f5a4172ac649

ChangeLog

@@ -1,3 +1,12 @@
+2010-09-05  Jay Berkenbilt  <ejb@ql.org>
+
+	* libqpdf/QPDF_Stream.cc (filterable): Handle inline image filter
+	abbreviations as stream filter abbreviations.  Although this is
+	not technically allowed by the PDF specification, table H.1 in the
+	pre-ISO spec indicates that Adobe's readers accept them.  Thanks
+	to Jian Ma <stronghorse@tom.com> for bringing this to my
+	attention.
+
 2010-08-14  Jay Berkenbilt  <ejb@ql.org>
 
 	* 2.2.0: release

libqpdf/QPDFWriter.cc

@@ -993,7 +993,9 @@ QPDFWriter::unparseObject(QPDFObjectHandle object, int level,
 	    // compressed with a lossy compression scheme, but we
 	    // don't support any of those right now.
 	    QPDFObjectHandle filter_obj = stream_dict.getKey("/Filter");
-	    if (filter_obj.isName() && (filter_obj.getName() == "/FlateDecode"))
+	    if (filter_obj.isName() &&
+		((filter_obj.getName() == "/FlateDecode") ||
+		 (filter_obj.getName() == "/Fl")))
 	    {
 		QTC::TC("qpdf", "QPDFWriter not recompressing /FlateDecode");
 		filter = false;

libqpdf/QPDF_Stream.cc

@@ -18,6 +18,8 @@
 
 #include <stdexcept>
 
+std::map<std::string, std::string> QPDF_Stream::filter_abbreviations;
+
 QPDF_Stream::QPDF_Stream(QPDF* qpdf, int objid, int generation,
 			 QPDFObjectHandle stream_dict,
 			 off_t offset, int length) :
@@ -93,6 +95,21 @@ QPDF_Stream::filterable(std::vector<std::string>& filters,
 			int& predictor, int& columns,
 			bool& early_code_change)
 {
+    if (filter_abbreviations.empty())
+    {
+	// The PDF specification provides these filter abbreviations
+	// for use in inline images, but according to table H.1 in the
+	// pre-ISO versions of the PDF specification, Adobe Reader
+	// also accepts them for stream filters.
+	filter_abbreviations["/AHx"] = "/ASCIIHexDecode";
+	filter_abbreviations["/A85"] = "/ASCII85Decode";
+	filter_abbreviations["/LZW"] = "/LZWDecode";
+	filter_abbreviations["/Fl"] = "/FlateDecode";
+	filter_abbreviations["/RL"] = "/RunLengthDecode";
+	filter_abbreviations["/CCF"] = "/CCITTFaxDecode";
+	filter_abbreviations["/DCT"] = "/DCTDecode";
+    }
+
     // Initialize values to their defaults as per the PDF spec
     predictor = 1;
     columns = 0;
@@ -243,7 +260,14 @@ QPDF_Stream::filterable(std::vector<std::string>& filters,
     for (std::vector<std::string>::iterator iter = filters.begin();
 	 iter != filters.end(); ++iter)
     {
-	std::string const& filter = *iter;
+	std::string& filter = *iter;
+
+	if (filter_abbreviations.count(filter))
+	{
+	    QTC::TC("qpdf", "QPDF_Stream expand filter abbreviation");
+	    filter = filter_abbreviations[filter];
+	}
+
 	if (! ((filter == "/Crypt") ||
 	       (filter == "/FlateDecode") ||
 	       (filter == "/LZWDecode") ||

libqpdf/qpdf/QPDF_Stream.hh

@@ -38,6 +38,8 @@ class QPDF_Stream: public QPDFObject
     void setObjGen(int objid, int generation);
 
   private:
+    static std::map<std::string, std::string> filter_abbreviations;
+
     void replaceFilterData(QPDFObjectHandle const& filter,
 			   QPDFObjectHandle const& decode_parms,
 			   size_t length);

qpdf/qpdf.testcov

@@ -185,3 +185,4 @@ QPDFObjectHandle prepend page contents 0
 QPDFObjectHandle append page contents 0
 QPDF_Stream getRawStreamData 0
 QPDF_Stream getStreamData 0
+QPDF_Stream expand filter abbreviation 0

qpdf/qtest/qpdf.test

@@ -111,7 +111,7 @@ $td->runtest("new stream",
 show_ntests();
 # ----------
 $td->notify("--- Miscellaneous Tests ---");
-$n_tests += 23;
+$n_tests += 25;
 
 $td->runtest("qpdf version",
 	     {$td->COMMAND => "qpdf --version"},
@@ -229,6 +229,16 @@ $td->runtest("C check version 2",
 	      $td->EXIT_STATUS => 0},
 	     $td->NORMALIZE_NEWLINES);
 
+# Stream filter abbreviations from table H.1
+$td->runtest("stream filter abbreviations",
+	     {$td->COMMAND => "qpdf --static-id filter-abbreviation.pdf a.pdf"},
+	     {$td->STRING => "",
+	      $td->EXIT_STATUS => 0},
+	     $td->NORMALIZE_NEWLINES);
+$td->runtest("check output",
+	     {$td->FILE => "a.pdf"},
+	     {$td->FILE => "filter-abbreviation.out"});
+
 show_ntests();
 # ----------
 $td->notify("--- Error Condition Tests ---");