目前，我正在从事一个使用 OpenCV3 进行实时视频处理(应用一组滤色器)的项目，我设法让它与 Java 一起工作，没有任何问题。

接下来我尝试做的是通过 NDK 将我所有的 Java 逻辑实现到 C++(以提高性能)。这样我就不需要将 MAT 对象来回转换为字节缓冲区，从而节省了几个周期。但我真的坚持尝试使用 gradle 链接 .so、.a 静态库和头文件以用于我的 .CPP 文件。

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')
}

我的 gradle 文件基于 this我在github上找到的例子。 现在，我在尝试这样做时发现的问题之一是 OPENCV 有几个静态库文件，因此 post说，我必须将每个添加到 gradle 的不同库中才能链接它们，所以这就是为什么我的 gradle 文件中充满了重复的库定义。

现在，当我尝试在我的 .CPP 代码中包含头文件时，Android Studio 找不到它们(甚至找不到要使用的命名空间)。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));
    }
}
}

为了正确链接它们，我是否遗漏了什么？

最佳答案

OpenCV 静态库之间存在依赖关系。因此，您需要以完全正确的顺序包含它们。 .a 和 .o includes 在 GCC 中依赖于顺序，具有依赖性的文件必须在它们依赖的文件之前包含:

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

关于Android Studio 链接 OpenCV 静态库，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/34701003/