tdf#106270 vcl PDF import: use BitmapWriteAccess::CopyScanline()

This requires one function call / row only, cross-platform and works
with OpenGL enabled as well.

Change-Id: I12fd0f52a1a7e8e683b50071ded95f63fecc4d40
Reviewed-on: https://gerrit.libreoffice.org/34774Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>

vcl/source/filter/ipdf/pdfread.cxx

@@ -73,34 +73,19 @@ bool generatePreview(SvStream& rStream, Graphic& rGraphic)
     FPDF_RenderPageBitmap(pPdfBitmap, pPdfPage, /*start_x=*/0, /*start_y=*/0, nPageWidth, nPageHeight, /*rotate=*/0, /*flags=*/0);
 
     // Save the buffer as a bitmap.
-    Bitmap aBitmap(Size(nPageWidth, nPageHeight), 32);
+    Bitmap aBitmap(Size(nPageWidth, nPageHeight), 24);
     {
         Bitmap::ScopedWriteAccess pWriteAccess(aBitmap);
-        auto pPdfBuffer = static_cast<const char*>(FPDFBitmap_GetBuffer(pPdfBitmap));
-#ifndef MACOSX
-        std::memcpy(pWriteAccess->GetBuffer(), pPdfBuffer, nPageWidth * nPageHeight * 4);
-#else
-        // ARGB -> BGRA
+        auto pPdfBuffer = static_cast<ConstScanline>(FPDFBitmap_GetBuffer(pPdfBitmap));
         for (size_t nRow = 0; nRow < nPageHeight; ++nRow)
         {
             int nStride = FPDFBitmap_GetStride(pPdfBitmap);
-            const char* pPdfLine = pPdfBuffer + (nStride * nRow);
-            Scanline pRow = pWriteAccess->GetBuffer() + (nPageWidth * nRow * 4);
-            for (size_t nCol = 0; nCol < nPageWidth; ++nCol)
-            {
-                pRow[nCol * 4] = pPdfLine[(nCol * 4) + 3];
-                pRow[(nCol * 4) + 1] = pPdfLine[(nCol * 4) + 2];
-                pRow[(nCol * 4) + 2] = pPdfLine[(nCol * 4) + 1];
-                pRow[(nCol * 4) + 3] = pPdfLine[nCol * 4];
-            }
+            ConstScanline pPdfLine = pPdfBuffer + (nStride * nRow);
+            // pdfium byte order is BGRA.
+            pWriteAccess->CopyScanline(nRow, pPdfLine, ScanlineFormat::N32BitTcBgra, nStride);
         }
-#endif
     }
-    BitmapEx aBitmapEx(aBitmap);
-#if defined(WNT) || defined(MACOSX)
-    aBitmapEx.Mirror(BmpMirrorFlags::Vertical);
-#endif
-    rGraphic = aBitmapEx;
+    rGraphic = aBitmap;
 
     FPDFBitmap_Destroy(pPdfBitmap);
     FPDF_ClosePage(pPdfPage);