diff -ruN dlib-19.6/dlib/CMakeLists.txt dlib-19.6-patched/dlib/CMakeLists.txt
--- dlib-19.6/dlib/CMakeLists.txt	2017-08-29 06:18:45.000000000 +0800
+++ dlib-19.6-patched/dlib/CMakeLists.txt	2017-08-31 22:17:53.862233903 +0800
@@ -146,7 +146,7 @@
       option(DLIB_LINK_WITH_SQLITE3 ${DLIB_LINK_WITH_SQLITE3_STR} ON)
       option(DLIB_USE_BLAS ${DLIB_USE_BLAS_STR} ON)
       option(DLIB_USE_LAPACK ${DLIB_USE_LAPACK_STR} ON)
-      option(DLIB_USE_CUDA ${DLIB_USE_CUDA_STR} ON)
+      option(DLIB_USE_CUDA ${DLIB_USE_CUDA_STR} OFF)
       option(DLIB_PNG_SUPPORT ${DLIB_PNG_SUPPORT_STR} ON)
       option(DLIB_GIF_SUPPORT ${DLIB_GIF_SUPPORT_STR} ON)
       #option(DLIB_USE_FFTW ${DLIB_USE_FFTW_STR} ON)
@@ -349,6 +349,7 @@
          if (PNG_FOUND AND LIBPNG_IS_GOOD)
             include_directories(${PNG_INCLUDE_DIR})
             set (dlib_needed_libraries ${dlib_needed_libraries} ${PNG_LIBRARIES})
+            set (dlib_needed_libraries ${dlib_needed_libraries} ${ZLIB_LIBRARIES})
             set(REQUIRES_LIBS " libpng")
          else()
             # If we can't find libpng then statically compile it in.