android - 找不到OpenCV Android C++写入

Question

我在Android应用中使用OpenCV C++
我的代码正在构建并运行良好，直到我添加此行cv::imwrite(result_uri, result_image)。
注意:cv:imread正在工作
错误是:error: undefined reference to 'cv::imwrite(cv::String const&, cv::_InputArray const&, std::__ndk1::vector<int, std::__ndk1::allocator<int> > const&)OpenCV 3.4.10，NDK 21
我想念什么？
谢谢
编辑
我正在使用Android.mk文件:

# ./android/app/src/main/jni/Android.mk

# Set up paths
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)

# Specify module name for System.loadLibrary() call
LOCAL_MODULE := helloworld
LOCAL_MODULE_SUFFIX := .so
LOCAL_MODULE_CLASS := SHARED_LIBRARIES

# Debug mode
NDK_DEBUG=1

# Specify C++ flags
LOCAL_CPPFLAGS := -std=c++17
LOCAL_CPPFLAGS += -fexceptions
LOCAL_CPPFLAGS += -frtti
LOCAL_CPPFLAGS += -Wall
LOCAL_CPPFLAGS += -Wextra
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../djinni/jni
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../djinni/cpp
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib/jni
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../src/cpp

# Specify source files
LOCAL_SRC_FILES += $(LOCAL_PATH)/../../../../../djinni/jni/NativeHelloWorld.cpp
LOCAL_SRC_FILES += $(wildcard $(LOCAL_PATH)/../../../../../src/cpp/*.cpp)
LOCAL_SRC_FILES += $(wildcard $(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib/jni/*.cpp)
LOCAL_SRC_FILES += $(wildcard $(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib/*.cpp)

# load opencv
OPENCVROOT:= /Users/Gasp/Library/OpenCV/OpenCV-android-sdk
OPENCV_CAMERA_MODULES:=off
OPENCV_INSTALL_MODULES:=on
OPENCV_LIB_TYPE:=SHARED
OPENCV_INSTALL_MODULES:=on
# LOCAL_STATIC_LIBRARIES += libopencv_contrib libopencv_legacy libopencv_ml libopencv_stitching libopencv_nonfree libopencv_objdetect libopencv_videostab libopencv_calib3d libopencv_photo libopencv_video libopencv_features2d libopencv_highgui libopencv_androidcamera libopencv_flann libopencv_imgproc libopencv_ts libopencv_core
include ${OPENCVROOT}/sdk/native/jni/OpenCV.mk


LOCAL_MODULE := helloworld

# Specify C++ flags
LOCAL_CPPFLAGS := -lopencv_imgcodecs
LOCAL_CPPFLAGS := -std=c++17
LOCAL_CPPFLAGS += -fexceptions
LOCAL_CPPFLAGS += -frtti
LOCAL_CPPFLAGS += -Wall
LOCAL_CPPFLAGS += -Wextra
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../djinni/jni
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../djinni/cpp
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib/jni
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../src/cpp


# Specify source files
LOCAL_SRC_FILES += $(LOCAL_PATH)/../../../../../djinni/jni/NativeHelloWorld.cpp
LOCAL_SRC_FILES += $(wildcard $(LOCAL_PATH)/../../../../../src/cpp/*.cpp)
LOCAL_SRC_FILES += $(wildcard $(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib/jni/*.cpp)
LOCAL_SRC_FILES += $(wildcard $(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib/*.cpp)


# Telling make to build the library
include $(BUILD_SHARED_LIBRARY)

Answer 1

我假设您使用CMake来构建OpenCV库。根据这个问题:undefined reference to 'cv::imwrite with Android NDK，需要添加一个编译器标志才能使此功能可用:-lopencv_imgcodecs。
在您的Android.mk文件中，只需确保将其附加到LOCAL_CPPFLAGS变量中即可:

# Specify C++ flags
LOCAL_CPPFLAGS := -std=c++17
LOCAL_CPPFLAGS += -lopencv_imgcodecs  # Note - change is here
LOCAL_CPPFLAGS += -fexceptions
LOCAL_CPPFLAGS += -frtti
LOCAL_CPPFLAGS += -Wall
LOCAL_CPPFLAGS += -Wextra
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../djinni/jni
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../djinni/cpp
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib/jni
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../node_modules/djinni/support-lib
LOCAL_CPPFLAGS += -I$(LOCAL_PATH)/../../../../../src/cpp

进行此更改后，请重新配置项目，然后尝试再次构建源。在尝试重新配置项目之前，请确保清除构建目录中的缓存，否则上面所做的更改将不会生效。