vcl: re-exporting broken pdfs -> empty pages

Certain pdf documents when loaded in LO_IMPORT_USE_PDFIUM=1 mode even if
pdf-version < v1.6 sometimes has missing objects referred by other
objects for determing its stream length for instance.  As a result
parsing fails and results in a pdf with empty pages.  A round trip
through pdfium and exporting to v1.6 seems to cure the issue. Possibly
it does some repairing work to determine the length of the stream in a
independent pass through the file.

Conflicts:
vcl/source/filter/ipdf/pdfread.cxx

Change-Id: Id09f67eddab4163ed12a3a3f3a73baf92e2912aa
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/141856
Tested-by: Jenkins
Reviewed-by: Dennis Francis <dennis.francis@collabora.com>

2 files changed, 43 insertions, 1 deletions

diff --git a/vcl/inc/pdf/ExternalPDFStreams.hxx b/vcl/inc/pdf/ExternalPDFStreams.hxx
index 7840217630c8..45b15f7a74bc 100644
--- a/vcl/inc/pdf/ExternalPDFStreams.hxx
+++ b/vcl/inc/pdf/ExternalPDFStreams.hxx
@@ -42,7 +42,7 @@ struct VCL_DLLPUBLIC ExternalPDFStream
             aPDFStream.WriteBytes(maDataContainer.getData(), maDataContainer.getSize());
             aPDFStream.Seek(0);
             auto pPDFDocument = std::make_shared<filter::PDFDocument>();
-            if (!pPDFDocument->Read(aPDFStream))
+            if (!pPDFDocument->ReadWithPossibleFixup(aPDFStream))
             {
                 SAL_WARN("vcl.pdfwriter",
                          "PDFWriterImpl::writeReferenceXObject: reading the PDF document failed");
diff --git a/vcl/inc/pdf/pdfcompat.hxx b/vcl/inc/pdf/pdfcompat.hxx
new file mode 100644
index 000000000000..8f629b3bc8ee
--- /dev/null
+++ b/vcl/inc/pdf/pdfcompat.hxx
@@ -0,0 +1,42 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include <config_features.h>
+#include <tools/gen.hxx>
+#include <tools/stream.hxx>
+#include <tools/UnitConversion.hxx>
+#include <vcl/graph.hxx>
+
+namespace vcl::pdf
+{
+/// Convert to inch, then assume 96 DPI.
+inline double pointToPixel(const double fPoint, const double fResolutionDPI)
+{
+    return o3tl::convert(fPoint, o3tl::Length::pt, o3tl::Length::in) * fResolutionDPI;
+}
+
+/// Decide if PDF data is old enough to be compatible.
+bool isCompatible(SvStream& rInStream, sal_uInt64 nPos, sal_uInt64 nSize);
+
+/// Converts to highest supported format version (currently 1.6).
+/// Usually used to deal with missing referenced objects in the
+/// source pdf stream.
+bool convertToHighestSupported(SvStream& rInStream, SvStream& rOutStream);
+
+/// Takes care of transparently downgrading the version of the PDF stream in
+/// case it's too new for our PDF export.
+bool getCompatibleStream(SvStream& rInStream, SvStream& rOutStream);
+
+BinaryDataContainer createBinaryDataContainer(SvStream& rStream);
+
+} // end of vcl::filter::ipdf namespace
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */