Reintroduce pkg-config with optional Makefile.config flag.

Makefile

@@ -329,7 +329,14 @@ NVCCFLAGS += -ccbin=$(CXX) -Xcompiler -fPIC $(COMMON_FLAGS)
 # mex may invoke an older gcc that is too liberal with -Wuninitalized
 MATLAB_CXXFLAGS := $(CXXFLAGS) -Wno-uninitialized
 LINKFLAGS += -pthread -fPIC $(COMMON_FLAGS) $(WARNINGS)
-LDFLAGS += $(foreach librarydir,$(LIBRARY_DIRS),-L$(librarydir)) \
+
+USE_PKG_CONFIG ?= 0
+ifeq ($(USE_PKG_CONFIG), 1)
+	PKG_CONFIG := $(shell pkg-config opencv --libs)
+else
+	PKG_CONFIG :=
+endif
+LDFLAGS += $(foreach librarydir,$(LIBRARY_DIRS),-L$(librarydir)) $(PKG_CONFIG) \
 		$(foreach library,$(LIBRARIES),-l$(library))
 PYTHON_LDFLAGS := $(LDFLAGS) $(foreach library,$(PYTHON_LIBRARIES),-l$(library))
 

Makefile.config.example

@@ -60,6 +60,10 @@ PYTHON_LIB := /usr/lib
 INCLUDE_DIRS := $(PYTHON_INCLUDE) /usr/local/include
 LIBRARY_DIRS := $(PYTHON_LIB) /usr/local/lib /usr/lib
 
+# Uncomment to use `pkg-config` to specify OpenCV library paths.
+# (Usually not necessary -- OpenCV libraries are normally installed in one of the above $LIBRARY_DIRS.)
+# USE_PKG_CONFIG := 1
+
 BUILD_DIR := build
 DISTRIBUTE_DIR := distribute