diff --color --unified --recursive --text caffe-ssd-1.0.orig/include/caffe/common.hpp caffe-ssd-1.0.new/include/caffe/common.hpp
--- caffe-ssd-1.0.orig/include/caffe/common.hpp	2018-01-02 20:07:58.000000000 +0100
+++ caffe-ssd-1.0.new/include/caffe/common.hpp	2021-11-21 17:01:19.980866883 +0100
@@ -69,6 +69,16 @@
 // is executed we will see a fatal log.
 #define NOT_IMPLEMENTED LOG(FATAL) << "Not Implemented Yet"
 
+// Supporting OpenCV4
+#if (CV_MAJOR_VERSION == 4)
+#define CV_LOAD_IMAGE_COLOR cv::IMREAD_COLOR
+#define CV_LOAD_IMAGE_GRAYSCALE cv::IMREAD_GRAYSCALE
+#define CV_CAP_PROP_FRAME_COUNT cv::CAP_PROP_FRAME_COUNT
+#define CV_CAP_PROP_POS_FRAMES cv::CAP_PROP_POS_FRAMES
+#define CV_FILLED cv::FILLED
+#define CV_FOURCC cv::VideoWriter::fourcc
+#endif
+
 // See PR #1236
 namespace cv { class Mat; }
 
diff --color --unified --recursive --text caffe-ssd-1.0.orig/Makefile caffe-ssd-1.0.new/Makefile
--- caffe-ssd-1.0.orig/Makefile	2021-11-21 16:59:16.379709144 +0100
+++ caffe-ssd-1.0.new/Makefile	2021-11-21 17:01:19.980866883 +0100
@@ -404,7 +404,7 @@
 CXXFLAGS += -MMD -MP
 
 # Complete build flags.
-COMMON_FLAGS += $(foreach includedir,$(INCLUDE_DIRS),-isystem $(includedir))
+COMMON_FLAGS += $(foreach includedir,$(INCLUDE_DIRS),-I $(includedir))
 CXXFLAGS += -pthread -fPIC $(COMMON_FLAGS) $(WARNINGS)
 NVCCFLAGS += -ccbin=$(CXX) -Xcompiler -fPIC $(COMMON_FLAGS)
 # mex may invoke an older gcc that is too liberal with -Wuninitalized
diff --color --unified --recursive --text caffe-ssd-1.0.orig/src/caffe/util/im_transforms.cpp caffe-ssd-1.0.new/src/caffe/util/im_transforms.cpp
--- caffe-ssd-1.0.orig/src/caffe/util/im_transforms.cpp	2018-01-02 20:07:58.000000000 +0100
+++ caffe-ssd-1.0.new/src/caffe/util/im_transforms.cpp	2021-11-21 17:05:01.293051919 +0100
@@ -1,7 +1,7 @@
 #ifdef USE_OPENCV
 #include <opencv2/highgui/highgui.hpp>
 
-#if CV_VERSION_MAJOR == 3
+#if CV_VERSION_MAJOR == 3 || CV_VERSION_MAJOR == 4
 #include <opencv2/imgcodecs/imgcodecs.hpp>
 #define CV_GRAY2BGR cv::COLOR_GRAY2BGR
 #define CV_BGR2GRAY cv::COLOR_BGR2GRAY
@@ -12,6 +12,13 @@
 #define CV_THRESH_BINARY_INV cv::THRESH_BINARY_INV
 #define CV_THRESH_OTSU cv::THRESH_OTSU
 #endif
+
+#if CV_VERSION_MAJOR == 4
+#define CV_BGR2HSV cv::COLOR_BGR2HSV
+#define CV_HSV2BGR cv::COLOR_HSV2BGR
+#define CV_BGR2Lab cv::COLOR_BGR2Lab
+#endif
+
 #endif  // USE_OPENCV
 
 #include <algorithm>