Rectified Cmake.

CMakeLists.txt

@@ -339,15 +339,19 @@ if (NOT STB_IMAGE_FOUND)
         # Now we have to also ensure these header files get installed.
         install(FILES ${CMAKE_BINARY_DIR}/deps/${STB_DIR}/stb_image.h DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
         install(FILES ${CMAKE_BINARY_DIR}/deps/${STB_DIR}/stb_image_write.h DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+        add_definitions(-DHAS_STB)
     else ()
       list(GET STB_IMAGE_DOWNLOAD_STATUS_LIST 1 STB_DOWNLOAD_ERROR)
-      message(FATAL_ERROR
+      message(WARNING
           "Could not download stb! Error code ${STB_DOWNLOAD_STATUS}: ${STB_DOWNLOAD_ERROR}!  Error log: ${STB_DOWNLOAD_LOG}")
     endif ()
   else ()
-    message(SEND_ERROR
-        "stb/stb_image.h not installed. Image utilites will not be available!")
+    message(WARNING
+        "stb/stb_image.h is not installed. Image utilites will not be available!")
   endif ()
+else ()
+  # Already has STB installed.
+  add_definitions(-DHAS_STB)
 endif ()
 
 # Find ensmallen.

src/mlpack/core/data/load_image.hpp

@@ -13,6 +13,8 @@
 #ifndef MLPACK_CORE_DATA_LOAD_IMAGE_HPP
 #define MLPACK_CORE_DATA_LOAD_IMAGE_HPP
 
+#ifdef HAS_STB // Compile this only if stb is present.
+
 #include <mlpack/core.hpp>
 #include <mlpack/core/util/log.hpp>
 #include <mlpack/prereqs.hpp>
@@ -204,4 +206,6 @@ class Image
 // Include implementation of Image.
 #include "load_image_impl.hpp"
 
-#endif
+#endif // HAS_STB.
+
+#endif 

src/mlpack/core/data/load_image_impl.hpp

@@ -13,6 +13,8 @@
 #ifndef MLPACK_CORE_DATA_LOAD_IMAGE_IMPL_HPP
 #define MLPACK_CORE_DATA_LOAD_IMAGE_IMPL_HPP
 
+#ifdef HAS_STB // Compile this only if stb is present.
+
 // In case it hasn't been included yet.
 #include "load_image.hpp"
 
@@ -302,4 +304,6 @@ bool Image::LoadDir(const std::string& dirPath,
 } // namespace data
 } // namespace mlpack
 
-#endif
+#endif // HAS_STB.
+
+#endif

src/mlpack/tests/image_load_test.cpp

@@ -17,6 +17,8 @@
 using namespace mlpack;
 using namespace std;
 
+#ifdef HAS_STB // Compile this only if stb is present.
+
 BOOST_AUTO_TEST_SUITE(ImageLoadTest);
 
 /**
@@ -160,3 +162,5 @@ BOOST_AUTO_TEST_CASE(SaveMultipleImageTest)
 }
 
 BOOST_AUTO_TEST_SUITE_END();
+
+#endif // HAS_STB.