How to Convert Graphic to File PNG

Converting existing image on a TImage (can be a TBitmap, TJPEG) into PNG format and then save them into PNG files.

Declaration procedure:
TImageToPNG procedure (Src: TImage; const Dst: String);
var
   PNG: TPNGObject;
   BMP: TBitmap;
begin
   PNG: = TPNGObject.Create;
   try
     / / If the TImage a TBitmap, directly converted to PNG
     if Src.Picture.Graphic is TBitmap then
       PNG.Assign (TBitmap (Src.Picture.Graphic))
     else
     begin
       / / If the TImage is not a TBitmap, the first convert to a TBitmap, and then to PNG
       BMP: = TBitmap.Create;
       try
         BMP.Assign (Src.Picture.Graphic);
         PNG.Assign (BMP);
       finally
         BMP.Free;
       end;
     end;
     / / Save a File
     PNG.SaveToFile (Dst);
   finally
     PNG.Free;
   end
end;

Make sure TPNGImage already integrated with your Delphi