diff --git a/CMakeLists.txt b/CMakeLists.txt
index d1954cb..f734306 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,6 +2,9 @@ project(vobsub2srt)
 
 cmake_minimum_required(VERSION 2.6.4 FATAL_ERROR)
 
+set(CMAKE_CXX_STANDARD 11)
+set(CMAKE_CXX_STANDARD_REQUIRED True)
+
 set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/CMakeModules)
 
 if(NOT CMAKE_BUILD_TYPE)
diff --git a/CMakeModules/FindTesseract.cmake b/CMakeModules/FindTesseract.cmake
index 4b15d74..36cf0fb 100644
--- a/CMakeModules/FindTesseract.cmake
+++ b/CMakeModules/FindTesseract.cmake
@@ -43,18 +43,8 @@ if(TESSERACT_DATA_PATH)
   add_definitions(-DTESSERACT_DATA_PATH="${TESSERACT_DATA_PATH}")
 endif()
 
-set(CMAKE_REQUIRED_INCLUDES ${Tesseract_INCLUDE_DIR})
-check_cxx_source_compiles(
-  "#include \"tesseract/baseapi.h\"
-   using namespace tesseract;
-   int main() {
-   }"
-  TESSERACT_NAMESPACE)
-if(TESSERACT_NAMESPACE)
-  add_definitions("-DCONFIG_TESSERACT_NAMESPACE")
-else()
-  message(WARNING "You are using an old Tesseract version. Support for Tesseract 2 is deprecated and will be removed in the future!")
-endif()
+add_definitions("-DCONFIG_TESSERACT_NAMESPACE")
+
 list(REMOVE_ITEM CMAKE_REQUIRED_INCLUDES ${Tesseract_INCLUDE_DIR})
 
 if(BUILD_STATIC)
diff --git a/src/vobsub2srt.c++ b/src/vobsub2srt.c++
index 2f9e1a0..1d49006 100644
--- a/src/vobsub2srt.c++
+++ b/src/vobsub2srt.c++
@@ -269,6 +269,22 @@ int main(int argc, char **argv) {
         dump_pgm(subname, sub_counter, width, height, stride, image, image_size);
       }
 
+      // for 4.x version use dark text on light background.
+      bool inverting_images = true;
+
+      if (inverting_images) {
+        int size_r = width * height;
+        unsigned char* image_rev = new unsigned char[size_r];
+        for (int i = 0; i < size_r; i++)
+        {
+            int val = static_cast<int>(image[i]);
+            unsigned char cz = (255 -  val);
+            image_rev[i] = cz;
+        }
+
+        image = image_rev;
+      }
+
 #ifdef CONFIG_TESSERACT_NAMESPACE
       char *text = tess_base_api.TesseractRect(image, 1, stride, 0, 0, width, height);
 #else