tdf#124752: Use best speed for PNG encoding on iOS

Still awfully slow for "realistic" images as taken by modern digital
cameras, though. It would be much better to not encode the PNG to put
on the clipboard from the internal bitmap representation, but use the
ooriginal PNG or JPEG data.

Change-Id: Ib72a573bd31d4ae7380dacccb4287e19afabb0d4

1 files changed, 17 insertions, 1 deletions

diff --git a/vcl/source/treelist/transfer.cxx b/vcl/source/treelist/transfer.cxx
index c9cf060a4fc7..3f7d7c5a655c 100644
--- a/vcl/source/treelist/transfer.cxx
+++ b/vcl/source/treelist/transfer.cxx
@@ -664,7 +664,23 @@ bool TransferableHelper::SetBitmapEx( const BitmapEx& rBitmapEx, const DataFlavo
         if(rFlavor.MimeType.equalsIgnoreAsciiCase("image/png"))
         {
             // write a PNG
-            vcl::PNGWriter aPNGWriter(rBitmapEx);
+            css::uno::Sequence<css::beans::PropertyValue> aFilterData;
+
+#ifdef IOS
+            // Use faster compression on slow devices
+            aFilterData.realloc(aFilterData.getLength() + 1);
+            aFilterData[aFilterData.getLength() - 1].Name = "Compression";
+
+            // We "know" that this gets passed to zlib's deflateInit2_(). 1 means best speed. For a
+            // typical 15 megapixel image from a DSLR, we are talking about a difference of 17 s for
+            // the default compression level vs 4 s for best speed, on an iPad Pro from 2017.
+            //
+            // Sure, the best would be to not have to re-encode the image at all, but have access to
+            // the original JPEG or PNG when there is a such.
+
+            aFilterData[aFilterData.getLength() - 1].Value <<= 1;
+#endif
+            vcl::PNGWriter aPNGWriter(rBitmapEx, &aFilterData);
 
             aPNGWriter.Write(aMemStm);
         }