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Android Studio 链接 OpenCV 静态库

androidc++opencvandroid-studioandroid-ndk
4

我目前正在处理一个使用OpenCV3进行实时视频处理的项目（应用一组颜色过滤器），并且成功地将其与Java配合使用。

接下来我想要做的是通过NDK将所有Java逻辑实现到C++中（以提高性能）。这样我就不需要在MAT对象和字节缓冲区之间进行转换，从而节省了一些循环。但是我真的卡在了尝试使用gradle链接.so、.a静态库和头文件以在我的.CPP文件中使用。

这是我正在使用的gradle文件：

apply plugin: 'com.android.model.application'

def opencvandroid_sdk_path = file(project(':opencvandroid').projectDir).absolutePath + "/src/main"

model {

    repositories {
        libs(PrebuiltLibraries) {
            opencv {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_calib3d.a")
                }
            }

            opencv1 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_core.a")
                }
            }

            opencv2 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_features2d.a")
                }
            }

            opencv3 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_flann.a")
                }
            }

            opencv4 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_highgui.a")
                }
            }

            opencv5 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_imgcodecs.a")
                }
            }

            opencv6 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_imgproc.a")
                }
            }

            opencv7 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_ml.a")
                }
            }

            opencv8 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_objdetect.a")
                }
            }

            opencv9 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_photo.a")
                }
            }

            opencv10 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_shape.a")
                }
            }

            opencv11 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_stitching.a")
                }
            }

            opencv12 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_superres.a")
                }
            }

            opencv13 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_video.a")
                }
            }

            opencv14 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_videoio.a")
                }
            }

            opencv15 {
                headers.srcDir "${opencvandroid_sdk_path}/jni/include/opencv2"
                binaries.withType(StaticLibraryBinary) {
                    staticLibraryFile = file("${opencvandroid_sdk_path}/jniLibs/${targetPlatform.getName()}/libopencv_videostab.a")
                }
            }
        }
    }

    android {
        compileSdkVersion = 23
        buildToolsVersion = "23.0.2"

        defaultConfig.with {
            applicationId = "com.example"
            minSdkVersion.apiLevel = 16
            targetSdkVersion.apiLevel = 23
            versionCode = 1
            versionName = "1.0"
        }
    }

    /*
     * native build settings
     */
    android.ndk {
        moduleName = "hello-jni"
        /*
         * Other ndk flags configurable here are
         * cppFlags += "-fno-rtti"
         * cppFlags += "-fno-exceptions"
         * ldLibs    = ["android", "log"]
         * stl       = "system"
         */
        platformVersion = 16 //same as minSdkVersion.apiLevel for better compatibility

        /*def jniPath = opencvandroid_sdk_path + "jniLibs"
        cppFlags += "-I${file(jniPath)}".toString()
        file(jniPath).eachDirRecurse { dir ->
            cppFlags += "-I${file(dir)}".toString()
        }*/

        stl = "c++_static"
        ldLibs.addAll(["atomic", "log", "android"])
    }

    android.sources {
        main {
            jni {
                dependencies {
                    library "opencv1" linkage "static"
                    library "opencv2" linkage "static"
                    library "opencv3" linkage "static"
                    library "opencv4" linkage "static"
                    library "opencv5" linkage "static"
                    library "opencv6" linkage "static"
                    library "opencv7" linkage "static"
                    library "opencv8" linkage "static"
                    library "opencv9" linkage "static"
                    library "opencv10" linkage "static"
                    library "opencv11" linkage "static"
                    library "opencv12" linkage "static"
                    library "opencv13" linkage "static"
                    library "opencv14" linkage "static"
                    library "opencv15" linkage "static"
                }
            }
        }
    }

    android.buildTypes {
        release {
            minifyEnabled = false
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile 'com.android.support:design:23.1.1'
    compile project(':opencvandroid')
}

我正在基于这个在github上找到的示例文件编写我的gradle文件。 现在，我发现一个问题是，OPENCV有一些静态库文件，因此根据此帖子所说，我必须在gradle中将每个库添加到不同的lib中以进行链接，因此导致我的gradle文件充斥着重复的库定义。
当我尝试在我的.cpp代码中包含头文件时，Android Studio找不到它们（甚至无法找到用于使用的名称空间）。这是我的CPP代码：
#include <jni.h>
#include "opencv2/core/core.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/features2d/features2d.hpp"
#include <vector>

using namespace std;
using namespace cv;

extern "C" {
JNIEXPORT void JNICALL Java_com_example_Tutorial2Activity_FindFeatures(JNIEnv*, jobject, jlong addrGray, jlong addrRgba);

JNIEXPORT void JNICALL Java_com_example_Tutorial2Activity_FindFeatures(JNIEnv*, jobject, jlong addrGray, jlong addrRgba)
{
    Mat& mGr  = *(Mat*)addrGray;
    Mat& mRgb = *(Mat*)addrRgba;
    vector<KeyPoint> v;

    Ptr<FeatureDetector> detector = FastFeatureDetector::create(50);
    detector->detect(mGr, v);
    for( unsigned int i = 0; i < v.size(); i++ )
    {
        const KeyPoint& kp = v[i];
        circle(mRgb, Point(kp.pt.x, kp.pt.y), 10, Scalar(255,0,0,255));
    }
}
}

我有点不确定是否还有什么遗漏，导致他们无法正确链接？
1
你引用了OpenCV静态库，这对于链接你的二进制文件非常重要。但是为了编译你的代码，你必须指定cppFlags。你为什么要注释掉那个带有def jniPath的部分？ - Alex Cohn
1
哦我的天啊，你是对的！我移除了cppFlags因为gradle无法读取配置文件...经过一番探索，我发现他们删除了+=赋值运算符，现在你必须使用.add和.addAll（作为对象），现在gradle可以找到所有头文件引用。自从我编译C++项目以来已经有一段时间了，忘记了这些标志。 - vicmns
@AlexCohn cppFlags变量应该放入什么内容？ - IgorGanapolsky
1
@IgorGanapolsky: C++编译中使用的所有标志都放在 cppFlags 中。使用 ndk-build 时，我们使用 APP_CPPFLAGS、LOCAL_CPPFLAGS 和 LOCAL_C_INCLUDES，这些都应该放在 cppFlags 中。请注意，+= 不起作用，请改用 .add。 - Alex Cohn
@AlexCohn 我使用了以下代码：cppFlags.addAll(['-std=c++11', '-fexceptions', '-frtti', '-Wno-error=format-security'])。然而，在我的静态库中仍然出现了未定义的引用错误。 - IgorGanapolsky
解决库问题，需要使用 ldLibs。 - Alex Cohn
1个回答
3

OpenCV静态库之间存在依赖关系。因此，您需要按照正确的顺序包含它们。在GCC中，.a和.o文件的包含顺序是有序的，具有依赖关系的文件必须在它们所依赖的文件之前被包含：

CV_LIBS = \
    $(CV_LIB_FOLDER)/libopencv_calib3d.a \
    $(CV_LIB_FOLDER)/libopencv_highgui.a \
    $(CV_LIB_FOLDER)/libopencv_video.a \
    $(CV_LIB_FOLDER)/libopencv_objdetect.a \
    $(CV_LIB_FOLDER)/libopencv_imgproc.a \
    $(CV_LIB_FOLDER)/libopencv_imgcodecs.a \
    $(CV_LIB_FOLDER)/libopencv_core.a \
    $(CV_LIB_FOLDER)/libopencv_hal.a
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