Related: tdf#106972 vcl PDF import: downgrade PDF >= 1.5

There are two problems with these newer PDF versions:

- the current PDF export code doesn't know how to roundtrip such PDF
  images (needs work on both the import and export side)
- upgrading the default PDF export version would upset readers who can't
  parse PDF >= 1.5

So instead of raising the default PDF export version, for now just be
conservative and depend on pdfium to downgrade the PDF image version to
1.4 if it would be higher.

Given that this modifies the input of the graphic filter this also needs
changes in the ODF export, so that the filter result will contain that
downgraded data, not the original one.

Change-Id: I1efa97af8110e9a6ee3e8a7339bcc7d70457cfb0
Reviewed-on: https://gerrit.libreoffice.org/36413
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>

1 files changed, 103 insertions, 4 deletions

diff --git a/vcl/source/filter/ipdf/pdfread.cxx b/vcl/source/filter/ipdf/pdfread.cxx
index b2f68d02b07e..f1a7e2b52a17 100644
--- a/vcl/source/filter/ipdf/pdfread.cxx
+++ b/vcl/source/filter/ipdf/pdfread.cxx
@@ -14,6 +14,7 @@
 #if HAVE_FEATURE_PDFIUM
 #include <fpdfview.h>
 #include <fpdf_edit.h>
+#include <fpdf_save.h>
 #endif
 
 #include <vcl/bitmapaccess.hxx>
@@ -25,6 +26,29 @@ namespace
 
 #if HAVE_FEATURE_PDFIUM
 
+/// Callback class to be used with FPDF_SaveWithVersion().
+struct CompatibleWriter : public FPDF_FILEWRITE
+{
+public:
+    CompatibleWriter();
+    static int WriteBlockCallback(FPDF_FILEWRITE* pFileWrite, const void* pData, unsigned long nSize);
+
+    SvMemoryStream m_aStream;
+};
+
+CompatibleWriter::CompatibleWriter()
+{
+    FPDF_FILEWRITE::version = 1;
+    FPDF_FILEWRITE::WriteBlock = CompatibleWriter::WriteBlockCallback;
+}
+
+int CompatibleWriter::WriteBlockCallback(FPDF_FILEWRITE* pFileWrite, const void* pData, unsigned long nSize)
+{
+    auto pImpl = static_cast<CompatibleWriter*>(pFileWrite);
+    pImpl->m_aStream.WriteBytes(pData, nSize);
+    return 1;
+}
+
 /// Convert to inch, then assume 96 DPI.
 double pointToPixel(double fPoint)
 {
@@ -88,6 +112,70 @@ bool generatePreview(SvStream& rStream, Graphic& rGraphic)
 
     return true;
 }
+
+/// Decide if PDF data is old enough to be compatible.
+bool isCompatible(SvStream& rInStream)
+{
+    // %PDF-x.y
+    sal_uInt8 aFirstBytes[8];
+    rInStream.Seek(STREAM_SEEK_TO_BEGIN);
+    sal_uLong nRead = rInStream.ReadBytes(aFirstBytes, 8);
+    if (nRead < 8)
+        return false;
+
+    if ((aFirstBytes[0] != '%' || aFirstBytes[1] != 'P' || aFirstBytes[2] != 'D' || aFirstBytes[3] != 'F' || aFirstBytes[4] != '-'))
+        return false;
+
+    sal_Int32 nMajor = OString(aFirstBytes[5]).toInt32();
+    sal_Int32 nMinor = OString(aFirstBytes[7]).toInt32();
+    if (nMajor > 1 || (nMajor == 1 && nMinor > 4))
+        return false;
+
+    return true;
+}
+
+/// 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)
+{
+    bool bCompatible = isCompatible(rInStream);
+    rInStream.Seek(STREAM_SEEK_TO_BEGIN);
+    if (bCompatible)
+        // Not converting.
+        rOutStream.WriteStream(rInStream);
+    else
+    {
+        // Downconvert to PDF-1.4.
+        FPDF_LIBRARY_CONFIG aConfig;
+        aConfig.version = 2;
+        aConfig.m_pUserFontPaths = nullptr;
+        aConfig.m_pIsolate = nullptr;
+        aConfig.m_v8EmbedderSlot = 0;
+        FPDF_InitLibraryWithConfig(&aConfig);
+
+        // Read input into a buffer.
+        SvMemoryStream aInBuffer;
+        aInBuffer.WriteStream(rInStream);
+
+        // Load the buffer using pdfium.
+        FPDF_DOCUMENT pPdfDocument = FPDF_LoadMemDocument(aInBuffer.GetData(), aInBuffer.GetSize(), /*password=*/nullptr);
+        if (!pPdfDocument)
+            return false;
+
+        CompatibleWriter aWriter;
+        // 14 means PDF-1.4.
+        if (!FPDF_SaveWithVersion(pPdfDocument, &aWriter, 0, 14))
+            return false;
+
+        FPDF_CloseDocument(pPdfDocument);
+        FPDF_DestroyLibrary();
+
+        aWriter.m_aStream.Seek(STREAM_SEEK_TO_BEGIN);
+        rOutStream.WriteStream(aWriter.m_aStream);
+    }
+
+    return rOutStream.good();
+}
 #else
 bool generatePreview(SvStream& rStream, Graphic& rGraphic)
 {
@@ -96,6 +184,13 @@ bool generatePreview(SvStream& rStream, Graphic& rGraphic)
 
     return true;
 }
+
+bool getCompatibleStream(SvStream& rInStream, SvStream& rOutStream)
+{
+    rInStream.Seek(STREAM_SEEK_TO_BEGIN);
+    rOutStream.WriteStream(rInStream);
+    return rOutStream.good();
+}
 #endif // HAVE_FEATURE_PDFIUM
 
 }
@@ -110,10 +205,14 @@ bool ImportPDF(SvStream& rStream, Graphic& rGraphic)
         return false;
 
     // Save the original PDF stream for later use.
-    rStream.Seek(STREAM_SEEK_TO_END);
-    uno::Sequence<sal_Int8> aPdfData(rStream.Tell());
-    rStream.Seek(STREAM_SEEK_TO_BEGIN);
-    rStream.ReadBytes(aPdfData.getArray(), aPdfData.getLength());
+    SvMemoryStream aMemoryStream;
+    if (!getCompatibleStream(rStream, aMemoryStream))
+        return false;
+
+    aMemoryStream.Seek(STREAM_SEEK_TO_END);
+    uno::Sequence<sal_Int8> aPdfData(aMemoryStream.Tell());
+    aMemoryStream.Seek(STREAM_SEEK_TO_BEGIN);
+    aMemoryStream.ReadBytes(aPdfData.getArray(), aPdfData.getLength());
     rGraphic.setPdfData(aPdfData);
 
     return true;