Continue cleaning.

src/image/png/PngWriter.cpp

@@ -126,7 +126,7 @@ void PngWriter::writeDataChunks(const BufferBitStream& buffer)
     auto max_bytes{32000};
 
     auto num_dat_chunks = num_bytes/max_bytes + 1;
-    unsigned offset = 0;
+    std::size_t offset = 0;
     for(std::size_t idx=0;idx<num_dat_chunks;idx++)
     {
         auto length = max_bytes;