tdf#137413 EMF import: fix transparency in the PDF fallback case

Commit d75c5b38911557173c54a78f42ff220ab3918573 (tdf#136836 emfio: speed
up import of EMF import when the orig PDF is available, 2020-09-17)
improved both performance and correctness of the EMF import, in case it
had a PDF fallback.

It turns out that PDF fallback can be nominally non-transparent, and
still the EMF equivalent supports transparency.

Fix the problem by enabling transparency in the PDF-in-EMF case.

Change-Id: I4d1585a5db6f28bd9c9cb380b5f193f4d5edcc8d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/104849
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins

4 files changed, 29 insertions, 3 deletions

diff --git a/emfio/inc/mtftools.hxx b/emfio/inc/mtftools.hxx
index 5c0c60973350..70471b66ea21 100644
--- a/emfio/inc/mtftools.hxx
+++ b/emfio/inc/mtftools.hxx
@@ -441,6 +441,7 @@ namespace emfio
         BitmapEx            aBmpEx;
         tools::Rectangle    aOutRect;
         sal_uInt32          nWinRop;
+        bool m_bForceAlpha = false;
 
         BSaveStruct(const Bitmap& rBmp, const tools::Rectangle& rOutRect, sal_uInt32 nRop)
             : aBmpEx(rBmp)
@@ -448,10 +449,12 @@ namespace emfio
             , nWinRop(nRop)
         {}
 
-        BSaveStruct(const BitmapEx& rBmpEx, const tools::Rectangle& rOutRect, sal_uInt32 nRop)
+        BSaveStruct(const BitmapEx& rBmpEx, const tools::Rectangle& rOutRect, sal_uInt32 nRop,
+                    bool bForceAlpha = false)
             : aBmpEx(rBmpEx)
             , aOutRect(rOutRect)
             , nWinRop(nRop)
+            , m_bForceAlpha(bForceAlpha)
         {}
     };
 
diff --git a/emfio/qa/cppunit/emf/EmfImportTest.cxx b/emfio/qa/cppunit/emf/EmfImportTest.cxx
index 9d3364693530..45894455141e 100644
--- a/emfio/qa/cppunit/emf/EmfImportTest.cxx
+++ b/emfio/qa/cppunit/emf/EmfImportTest.cxx
@@ -26,6 +26,7 @@
 
 #include <drawinglayer/primitive2d/baseprimitive2d.hxx>
 #include <drawinglayer/tools/primitive2dxmldump.hxx>
+#include <vcl/bitmapaccess.hxx>
 
 #include <memory>
 
@@ -243,6 +244,20 @@ void Test::TestPdfInEmf()
     // i.e. there was no size hint, the shape with 14cm height had a bitmap-from-PDF fill, the PDF
     // height was only 5cm, so it looked blurry.
     CPPUNIT_ASSERT_EQUAL(14321.0, pVectorGraphicData->getSizeHint().getY());
+
+#if !defined(WNT) && !defined(MACOSX)
+    // Hmm, manual testing on Windows looks OK.
+    BitmapEx aBitmapEx = aGraphic.GetBitmapEx();
+    AlphaMask aMask = aBitmapEx.GetAlpha();
+    Bitmap::ScopedReadAccess pAccess(aMask);
+    Color aColor(pAccess->GetPixel(0, 0));
+    // Without the accompanying fix in place, this test would have failed with:
+    // - Expected: 220
+    // - Actual  : 0
+    // i.e. the pixel at the top left corner was entirely opaque, while it should be mostly
+    // transparent.
+    CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt8>(220), aColor.GetBlue());
+#endif
 }
 
 CPPUNIT_TEST_SUITE_REGISTRATION(Test);
diff --git a/emfio/source/reader/emfreader.cxx b/emfio/source/reader/emfreader.cxx
index b47d0c86496f..1bc6339ff897 100644
--- a/emfio/source/reader/emfreader.cxx
+++ b/emfio/source/reader/emfreader.cxx
@@ -507,7 +507,8 @@ namespace emfio
         // ours.
         aGraphic.getVectorGraphicData()->setSizeHint(maSizeHint);
 
-        maBmpSaveList.emplace_back(new BSaveStruct(aGraphic.GetBitmapEx(), aOutputRect, SRCCOPY));
+        maBmpSaveList.emplace_back(
+            new BSaveStruct(aGraphic.GetBitmapEx(), aOutputRect, SRCCOPY, /*bForceAlpha=*/true));
         const std::shared_ptr<VectorGraphicData> pVectorGraphicData
             = aGraphic.getVectorGraphicData();
         if (!pVectorGraphicData)
diff --git a/emfio/source/reader/mtftools.cxx b/emfio/source/reader/mtftools.cxx
index e32b0f2be502..7cd1ff58093d 100644
--- a/emfio/source/reader/mtftools.cxx
+++ b/emfio/source/reader/mtftools.cxx
@@ -1837,7 +1837,14 @@ namespace emfio
                             {
                                 if ( nRasterOperation == 0x33 )
                                     aBitmap.Invert();
-                                ImplDrawBitmap( aPos, aSize, BitmapEx(aBitmap) );
+                                if (pSave->m_bForceAlpha)
+                                {
+                                    ImplDrawBitmap(aPos, aSize, pSave->aBmpEx);
+                                }
+                                else
+                                {
+                                    ImplDrawBitmap(aPos, aSize, BitmapEx(aBitmap));
+                                }
                             }
                             break;