Further compression and png work.

src/image/PngWriter.h

@@ -8,19 +8,31 @@
 
 using Path = std::filesystem::path;
 
+class BitStream;
+class File;
+
 class PngWriter
 {
 public:
     PngWriter();
+    ~PngWriter();
 
     static std::unique_ptr<PngWriter> Create();
 
     void setPath(const Path& path);
 
-    void write(const std::unique_ptr<Image<unsigned char> >& image) const;
+    void write(const std::unique_ptr<Image<unsigned char> >& image);
 
 private:
+    void writeSignature();
+    void writeHeader();
+
+
     Path mPath;
+    Image<unsigned char>* mWorkingImage{nullptr};
+    std::unique_ptr<BitStream> mInStream;
+    std::unique_ptr<BitStream> mOutStream;
+    std::unique_ptr<File> mWorkingFile;
 };
 
 using PngWriterPtr = std::unique_ptr<PngWriter>;