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// (De-)Compress functions
procedure CompressStream(aSource,aTarget:TStream);
var
	compStream:TCompressionStream;
begin
  compStream:=TCompressionStream.Create(clFastest,aTarget);
  try
    aSource.Position:=0;
    compStream.CopyFrom(aSource,aSource.Size);
    compStream.CompressionRate;
  finally
    compStream.Free;
  end;
end;

procedure DecompressStream(aSorce,aTarget:TStream);
var
	decompStream:TDecompressionStream;
  nRead:integer;
  Buffer:array[0..1023] of Char;
  Count:integer;
begin
  decompStream:=TDecompressionStream.Create(aSorce);
  try
    if aSorce.Size > 0 then begin
      decompStream.Position:=0;
      Count:=1024;
      repeat

        try
          nRead:=decompStream.Read(Buffer,Count);
        except
          on E:Exception do begin
            raise Exception.Create('Decompression error when write ir to stream!');
          end;
        end;

        try
          aTarget.WriteBuffer(Buffer,nRead);
        except
          on E:Exception do begin
            raise Exception.Create('Decompression error when write ir to stream!');
          end;
        end;

      until nRead=0;
    end;
  finally
    decompStream.Free;
  end;
end;

procedure ReadBlobField(ImageField:TBlobField;Image:TImage;DeCompress:boolean);
var
  memoStream:TMemoryStream;
  compStream:TMemoryStream;
begin
	if ImageField.IsNull then begin
   	memoStream:=TMemoryStream.Create;
    Image.AutoSize:=true;
    Image.Picture.Bitmap.LoadFromStream(memoStream);
    Image.AutoSize:=false;
		exit;
	end;

  memoStream:=TMemoryStream.Create;
  if DeCompress then compStream:=TMemoryStream.Create else compStream:=nil;

  try
    // blob kiolvasása

    (* DbExpress
    bstream:=TSQLBlobStream.Create(ImageField,bmReadWrite);
    bstream.ReadBlobData;
    bstream.Position:=0;
    try
      if DeCompress then begin
        compStream.LoadFromStream(bstream);
        compStream.Position:=0;
        DecompressStream(compStream,memoStream);
      end else begin
        memoStream.LoadFromStream(bstream);
      end;
    except
      on E:Exception do begin
        ShowPSError('Blob field reading error: '+#10+E.Message);
        memoStream.Size:=0;
        if DeCompress then compStream.Size:=0;
      end;
    end;
    bstream.Free;
    *)
    try
      if DeCompress then begin
        ImageField.SaveToStream(compStream);
        compStream.Position:=0;
        DecompressStream(compStream,memoStream);
      end else begin
        ImageField.SaveToStream(memoStream);
      end;
    except
      on E:Exception do begin
        ShowPSError('Blob field reading error: '+#10+E.Message);
        memoStream.Size:=0;
        if DeCompress then compStream.Size:=0;
      end;
    end;


    try
      Image.AutoSize:=true;
      memoStream.Position:=0;
      Image.Picture.Bitmap.FreePixmap;
      Image.Picture.Bitmap.FreeImage;
      if memoStream.Size>0 then begin
        memoStream.Position:=0;
        Image.Picture.Bitmap.LoadFromStream(memoStream);
      end;
      Image.AutoSize:=false;
    except
      on E:Exception do ShowPSError('Image creating error: '+#10+E.Message);
    end;
  finally
     memoStream.Free;
     if DeCompress then compStream.Free;
  end;
end;

procedure WriteBlobParam(ImageParam:TParam;Image:TImage;Compress:boolean);
var
	memoStream:TMemoryStream;
	compStream:TMemoryStream;
begin
	memoStream:=TMemoryStream.Create;
	if Compress then compStream:=TMemoryStream.Create else compStream:=nil;
	try
		Image.Picture.Bitmap.SaveToStream(memoStream);
		if memoStream.Size=0 then begin
      if AnsiContainsText(DM.conDB.Protocol,'mssql') or
        (AnsiContainsText(DM.conDB.Database, 'SQLOLEDB')) then begin
			  ImageParam.Value:=0
      end else begin
        ImageParam.Value:=Null;
        // ImageParam.LoadFromStream(memoStream,ImageParam.DataType);
      end;
		end else begin
			// memoStream.Size;
			memoStream.Position:=0;
      if Compress then begin
        CompressStream(memoStream,compStream);
        compStream.Position:=0;
        ImageParam.LoadFromStream(compStream,ImageParam.DataType);
      end else begin
        memoStream.Position:=0;
        ImageParam.LoadFromStream(memoStream,ImageParam.DataType);
      end;
      memoStream.Position:=0;
		end;
	finally
		memoStream.Free;
		if Compress then compStream.Free
	end;
end;