未找到 OpenCV Android C++ imwrite

Question

我在我的安卓应用中使用 OpenCV C++

我的代码正在构建并且运行良好，直到我添加了这一行 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

我错过了什么？ 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您的 LOCAL_CPPFLAGS 变量：

# 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

完成此更改后，重新配置项目并尝试再次构建源代码。确保在尝试重新配置项目之前清除构建目录中的缓存，否则上面所做的更改将不会生效。

Answer 2

其他尝试：

我尝试切换到 OpenCV android 4.3.0。

在构建期间没有更多关于未定义引用的错误。

在运行时悬停该行：

frame = cv::imread(trim_uri_protocal(uri), cv::IMREAD_COLOR);

（同时适用于 OpenCV android 3.4.10 和 iOS 上的 OpenCV）

导致此错误 E/libc++abi: terminating with uncaught exception of type std::bad_cast: std::bad_cast

也许一个想法来解决这个问题？