Implement check for Tensorflow header file

This looks for one of the header files which are included by Tesseract.
It currently uses a hard coded path which works for Debian / Ubuntu.

Simplify also the rules for linking Tensorflow.

Signed-off-by: Stefan Weil <sw@weilnetz.de>

configure.ac

@@ -196,13 +196,23 @@ if test "$enable_opencl" = "yes"; then
 fi
 
 # Check whether to build with support for Tensorflow.
-AC_MSG_CHECKING([--with-tensorflow])
 AC_ARG_WITH([tensorflow],
   AS_HELP_STRING([--with-tensorflow],
                  [support Tensorflow @<:@default=check@:>@]),
   [], [with_tensorflow=check])
-AC_MSG_RESULT([$with_tensorflow])
-AM_CONDITIONAL([TENSORFLOW], [test "$with_tensorflow" != "no"])
+AM_CONDITIONAL([TENSORFLOW], false)
+TENSORFLOW_LIBS=
+AS_IF([test "x$with_tensorflow" != xno],
+  [AC_CHECK_FILE([/usr/include/tensorflow/core/framework/graph.pb.h],
+    [AC_SUBST([TENSORFLOW_LIBS], ["-lprotobuf -ltensorflow_cc"])
+      AM_CONDITIONAL([TENSORFLOW], true)
+    ],
+    [if test "x$with_tensorflow" != xcheck; then
+      AC_MSG_FAILURE(
+        [--with-tensorflow was given, but test for libtensorflow-dev failed])
+     fi
+    ])
+  ])
 
 # https://lists.apple.com/archives/unix-porting/2009/Jan/msg00026.html
 m4_define([MY_CHECK_FRAMEWORK],

src/api/Makefile.am

@@ -88,6 +88,7 @@ tesseract_LDFLAGS = $(OPENCL_LDFLAGS)
 
 tesseract_LDADD += $(LEPTONICA_LIBS)
 tesseract_LDADD += $(OPENMP_CXXFLAGS)
+tesseract_LDADD += $(TENSORFLOW_LIBS)
 tesseract_LDADD += $(libarchive_LIBS)
 
 if T_WIN
@@ -98,8 +99,3 @@ endif
 if ADD_RT
 tesseract_LDADD += -lrt
 endif
-
-if TENSORFLOW
-tesseract_LDADD += -lprotobuf
-tesseract_LDADD += -ltensorflow_cc
-endif

src/training/Makefile.am

@@ -282,9 +282,7 @@ unicharset_extractor_LDADD += $(LEPTONICA_LIBS)
 wordlist2dawg_LDADD += $(LEPTONICA_LIBS)
 
 extralib = $(libarchive_LIBS)
-if TENSORFLOW
-extralib += -lprotobuf -ltensorflow_cc
-endif
+extralib += $(TENSORFLOW_LIBS)
 
 if !DISABLED_LEGACY_ENGINE
 ambiguous_words_LDADD += $(extralib)