procedure TForm1.Button1Click(Sender: TObject);
var
 InputStream:TMemoryStream;
 OutputStream:TStringStream;
begin
 InputStream:=TMemoryStream.Create;
  try
   InputStream.LoadFromFile('C:\File.jpg');
    OutputStream:=TStringStream.Create;
     try
      TNetEncoding.Base64.Encode(InputStream, OutputStream);
      ShowMessage(OutputStream.DataString);

     finally
      OutputStream.Free;
     end;
  finally
    InputStream.Free;
  end;
end;

function TSchedulerFrm.GetResourcesJSONArr: string;
  var JSONArr     : TJSONArray;
      JSONObj     : TJSONObject;
      InputStream :TMemoryStream;
      OutputStream:TStringStream;
begin
  JSONArr := TJSONArray.Create;
  try
    FResourceCacheEdit.First;
    while not FResourceCacheEdit.Eof do
    begin
      if FResourceCacheEdit.Edited = True then
      begin
        JSONObj := TJSONObject.Create;
       ..
       ..
        

        if not FResourceCacheEdit.MSEV1Miniature.isNULL then
        begin
          InputStream := TMemoryStream.Create;
          try
            FResourceCacheEdit.MSEV1Miniature.SaveToStream(InputStream);
            InputStream.Position := 0;

            OutputStream := TStringStream.Create;
            try
              TNetEncoding.Base64.Encode(InputStream, OutputStream);
              JSONObj.AddPair(TJSONPair.Create(fnSCH_MSEV1Miniature,      OutputStream.DataString));
            finally
              OutputStream.Free;
            end;
          finally
            InputStream.Free;
          end;
        end;

        // Сохраняем объект в массив.
        JSONArr.AddElement(JSONObj);
      end;

      FResourceCacheEdit.Next;
    end;

    Result := JSONArr.ToString;
  finally
    JSONArr.Free;
  end;
end;

 SELECT
	  [MSEV1Miniature]
 FROM OPENJSON(@ResourcesJSONArr) WITH (
      
      [MSEV1Miniature]				VARBINARY(MAX)	'$.MSEV1Miniature'
    )

DECLARE @Json VARCHAR(MAX) = 
'[
    {
        "ID": 1,
        "Data": "SGVsbG8gd29ybGQh"
    }
 ]'
 
SELECT ID, [Data], CONVERT(VARCHAR(MAX), [Data]) as EncodedText
  
 FROM OPENJSON(@Json)
 WITH
  (
   ID int,
   [Data] VARBINARY(MAX)
  )

TBase64Encoding.Create(-1, '')