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简述
我们通过java sdk的方式已经将opencv接入到项目中了，如果想使用opencv sdk 提供的 c++ 头文件与 .so动态库,自己封装jni这样使用上篇的方式显然是不能实现的。所以本篇我们介绍通过cmake的方式接入opencv。
接入步骤
1、新建jni项目
具体创建过程参考上篇：通过java sdk方式接入opencv 。
2、导入so库
在项目app/src/main目录下新建jnilibs，并将解压后的opencv sdk 目录下对应的路径 sdk/native/libs 中的文件复制到jnilibs中。
2、导入cpp文件
将opencv sdk 目录下对应的路径 sdk/native/jni/include 中的文件复制到cpp目录中。
3、修改cmakelists
将src/main/cpp 中的cmakelists移动到app目录下。
2.修改cmakelists中的内容
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# for more information about using cmake with android studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
# 设置cmake的版本号
cmake_minimum_required(version 3.4.1)
# 设置include文件夹的地址
include_directories(${cmake_source_dir}/src/main/cpp/include)
# 设置opencv的动态库
add_library(libopencv_java4 shared imported)
set_target_properties(libopencv_java4 properties imported_location
${cmake_source_dir}/src/main/jnilibs/${android_abi}/libopencv_java4.so)
add_library( # sets the name of the library.
native-lib #.so库名 可自定义
# sets the library as a shared library.
shared
# provides a relative path to your source file(s).
src/main/cpp/native-lib.cpp)
find_library( # sets the name of the path variable.
log-lib
# specifies the name of the ndk library that
# you want cmake to locate.
log)
target_link_libraries( # specifies the target library.
native-lib
libopencv_java4
# links the target library to the log library
# included in the ndk.
${log-lib})
修改app 中的build.gradle文件 defaultconfig 中配置cmake和ndk
externalnativebuild {
cmake {
cppflags "-std=c++11"
arguments "-dandroid_stl=c++_shared"
}
}
ndk{
abifilters "armeabi-v7a","arm64-v8a"
}
android 中配置jnilibs
sourcesets{
main{
jnilibs.srcdirs = ['src/main/jnilibs']
}
}
android 中配置cmake和ndk相关
externalnativebuild {
cmake {
path file('cmakelists.txt')
version "3.10.2"
}
}
splits {
abi {
enable true
reset()
include 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a' //select abis to build apks for
universalapk true //generate an additional apk that contains all the abis
}
}
如果是老项目则不必配置splits否则会报错，只需要干掉下面的代码
splits {
abi {
enable true
reset()
include 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a' //select abis to build apks for
universalapk true //generate an additional apk that contains all the abis
}
}
最终配置完的代码为：
apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
android {
compilesdkversion 29
defaultconfig {
applicationid "com.jd.opencv"
minsdkversion 23
targetsdkversion 29
versioncode 1
versionname "1.0"
testinstrumentationrunner "androidx.test.runner.androidjunitrunner"
externalnativebuild {
cmake {
cppflags "-std=c++11"
arguments "-dandroid_stl=c++_shared"
}
}
ndk{
abifilters "armeabi-v7a","arm64-v8a"
}
}
sourcesets{
main{
jnilibs.srcdirs = ['src/main/jnilibs']
}
}
buildtypes {
release {
minifyenabled false
proguardfiles getdefaultproguardfile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
externalnativebuild {
cmake {
path file('cmakelists.txt')
version "3.10.2"
}
}
splits {
abi {
enable true
reset()
include 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a' //select abis to build apks for
universalapk true //generate an additional apk that contains all the abis
}
}
project.ext.versioncodes = ['armeabi': 1, 'armeabi-v7a': 2, 'arm64-v8a': 3, 'mips': 5, 'mips64': 6, 'x86': 8, 'x86_64': 9]
android.applicationvariants.all { variant ->
variant.outputs.each { output ->
output.versioncodeoverride =
project.ext.versioncodes.get(output.getfilter(com.android.build.outputfile.abi), 0) * 1000000 + android.defaultconfig.versioncode
}
}
}
dependencies {
implementation filetree(dir: 'libs', include: ['*.jar'])
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
implementation 'androidx.appcompat:appcompat:1.1.0'
implementation 'androidx.core:core-ktx:1.2.0'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
testimplementation 'junit:junit:4.12'
androidtestimplementation 'androidx.test.ext:junit:1.1.1'
androidtestimplementation 'androidx.test.espresso:espresso-core:3.2.0'
}
使用
我们将一张彩色图片通过 opencv 处理成一张灰色的照片。
1、编写处理照片的代码。
创建native代码
object nativelibutils{
init {
system.loadlibrary("native-lib")
}
external fun bitmap2grey(pixels: intarray, w: int, h: int): intarray
}
创建 jni 代码
#include <jni.h>
#include <jni.h>
#include <string>
#include<opencv2/opencv.hpp>
#include<iostream>
#include <opencv2/imgproc/types_c.h>
#include <unistd.h>
using namespace cv;
using namespace std;
extern "c"
jniexport jintarray jnicall
java_com_mp5a5_opencv_nativelibutils_bitmap2gray(jnienv *env, jobject instance, jintarray pixels,
jint w, jint h) {
jint *cur_array;
jboolean iscopy = static_cast<jboolean>(false);
cur_array = env->getintarrayelements(pixels, &iscopy);
if (cur_array == null) {
return 0;
}
mat img(h, w, cv_8uc4, (unsigned char *) cur_array);
cvtcolor(img, img, cv_bgra2gray);
cvtcolor(img, img, cv_gray2bgra);
int size = w * h;
jintarray result = env->newintarray(size);
env->setintarrayregion(result, 0, size, (jint *) img.data);
env->releaseintarrayelements(pixels, cur_array, 0);
return result;
}
调用 native 代码来实现彩色图片转换成灰色图片
private fun showgrayimg() {
val w = bitmap.width
val h = bitmap.height
val pixels = intarray(w * h)
bitmap.getpixels(pixels, 0, w, 0, 0, w, h)
val resultdata: intarray = nativelibutils.bitmap2gray(pixels, w, h)
val resultimage = bitmap.createbitmap(w, h, bitmap.config.argb_8888)
resultimage.setpixels(resultdata, 0, w, 0, 0, w, h)
iv_image.setimagebitmap(resultimage)
}
完整转换的代码
class opencvactivity : appcompatactivity(), view.onclicklistener {
private lateinit var bitmap: bitmap
override fun oncreate(savedinstancestate: bundle?) {
super.oncreate(savedinstancestate)
setcontentview(r.layout.activity_opencv)
bitmap = bitmapfactory.decoderesource(resources, r.mipmap.person)
iv_image.setimagebitmap(bitmap)
btn_btn1.setonclicklistener(this)
btn_btn2.setonclicklistener(this)
}
override fun onclick(v: view?) {
v?.id?.let {
when (it) {
r.id.btn_btn1 -> {
showgrayimg()
}
r.id.btn_btn2 -> {
showrgbimg()
}
}
}
}
private fun showrgbimg() {
bitmap = bitmapfactory.decoderesource(resources, r.mipmap.person)
iv_image.setimagebitmap(bitmap)
}
private fun showgrayimg() {
val w = bitmap.width
val h = bitmap.height
val pixels = intarray(w * h)
bitmap.getpixels(pixels, 0, w, 0, 0, w, h)
val resultdata: intarray = nativelibutils.bitmap2gray(pixels, w, h)
val resultimage = bitmap.createbitmap(w, h, bitmap.config.argb_8888)
resultimage.setpixels(resultdata, 0, w, 0, 0, w, h)
iv_image.setimagebitmap(resultimage)
}
}
<?xml version="1.0" encoding="utf-8"?>
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".mainactivity">
<imageview
android:id="@+id/iv_image"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_above="@id/ll_location"
app:srccompat="@mipmap/person" />
<linearlayout
android:id="@+id/ll_location"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignparentbottom="true"
android:orientation="horizontal">
<button
android:id="@+id/btn_btn1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="灰度图" />
<button
android:id="@+id/btn_btn2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="色图" />
</linearlayout>
</relativelayout>
显示效果：
效果图
demo 的 github 地址 https://github.com/mp5a5/androidopencv
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