PDF export: skip pointless downsampling for very small images

Regression from commit b6588bd7c831ce88a29131ca7ea8d3f3e082564e (Reduce
image resolution by default in PDF Export, 2014-03-02) the problem is
that in case you have small enough bitmaps, then these used to look
OK at reasonable zoom levels, but now we intentionally scale down
bitmaps by default.

That makes little sense for tiny images, do this only for large ones.

(cherry picked from commit b894ec7fadb8ca6bf0b33fa9eee4b9303e8161d4)

[ Testcase not backported, pdfium is too old on this branch. ]

Conflicts:
vcl/qa/cppunit/pdfexport/pdfexport.cxx
vcl/source/gdi/pdfwriter_impl2.cxx

Change-Id: Iff15325b842b47d9285a7c0f83f402897498392d

1 files changed, 4 insertions, 2 deletions

diff --git a/vcl/source/gdi/pdfwriter_impl2.cxx b/vcl/source/gdi/pdfwriter_impl2.cxx
index bf039f142d58..26cfe00c9b27 100644
--- a/vcl/source/gdi/pdfwriter_impl2.cxx
+++ b/vcl/source/gdi/pdfwriter_impl2.cxx
@@ -104,11 +104,13 @@ void PDFWriterImpl::implWriteBitmapEx( const Point& i_rPoint, const Size& i_rSiz
             bIsPng = (eType == GfxLinkType::NativePng);
         }
 
-        if( i_rContext.m_nMaxImageResolution > 50 )
+        // Do not downsample images smaller than 50x50px.
+        const Size      aBmpSize( aBitmapEx.GetSizePixel() );
+        if (i_rContext.m_nMaxImageResolution > 50 && aBmpSize.getWidth() > 50
+                && aBmpSize.getHeight() > 50)
         {
             // do downsampling if necessary
             const Size      aDstSizeTwip( i_pDummyVDev->PixelToLogic( i_pDummyVDev->LogicToPixel( aSize ), MapUnit::MapTwip ) );
-            const Size      aBmpSize( aBitmapEx.GetSizePixel() );
             const double    fBmpPixelX = aBmpSize.Width();
             const double    fBmpPixelY = aBmpSize.Height();
             const double    fMaxPixelX = aDstSizeTwip.Width() * i_rContext.m_nMaxImageResolution / 1440.0;