Android passing file path to OpenCV imread method -

-

i trying use opencv in android project , trying run native code don't know how use parameter

jniexport jint jnicall java_com_example_helloopencvactivity_nativecalls_filepath     (jnienv * env, jobject jo, jstring str1, jstring str2) {     cv::mat img1 = cv::imread(""); }

i tried using this

const char *nativestring = (*env)->getstringutfchars(env, str1, 0); cv::mat img1 = cv::imread(nativestring);

but getting error error: no matching function call '_jnienv::getstringutfchars

i need pass file path android file system opencv's native code processing, passing element string , should read imread

first in java side, codes looks like：

 private string path="/mnt/sdcard/";   initfeature(width,height,path);   public native void initfeature(int width, int height,string path);

then in jni side, it's:

//passed java part , release after initfreature const char* npath; //to save globle path char* g_path;  jniexport void jnicall java_org_opencv_samples_tutorial6_tutorial2activity_initfeature(jnienv* env, jobject,jint width,jint height,jstring path);  jniexport void jnicall java_org_opencv_samples_tutorial6_tutorial2activity_initfeature(jnienv* env, jobject,jint width,jint height,jstring path) {  //jsize path_size; npath=env->getstringutfchars(path,null); //path_size=env->getarraylength(path);  logd("path: %s \n",npath);  int length=strlen(npath);  logd("length: %d \n",length);  g_path=new char[length+1];  memcpy(g_path,npath,length+1);  logd("path_2: %s \n",g_path); logd("length: %d \n",strlen(g_path));  char l_path[128];  strcpy(l_path,g_path); strcat(l_path,"color.jpg");  logd("path_3: %s \n",l_path); logd("length: %d \n",sizeof(l_path));  m_width=width; m_height=height;  center.x=float (m_width/2.0+0.5);//float (img_tmp->width/2.0+0.5); center.y=float (m_width/2.0+0.5);//float (img_tmp->height/2.0+0.5);      env->releasestringutfchars(path,npath);  }

since have different native calls, 1 initiate features(shown here) , others process every frame, , after env->releasestringutfchars(path,npath); string invisible jni part. have copy string global char* g_path;

and little sample here well, file path "/mnt/sdcard/color.jpg" , check logs.

then can use imread() jpg. use other libs libjpg, not showing codes here.


Comments

Post a Comment

Popular posts from this blog

c# - How Configure Devart dotConnect for SQLite Code First? -

-
can configure following sample code ? when run following code, error : no entity framework provider found ado.net provider invariant name 'devart.data.sqlite' setting in machine.config <system.data> <dbproviderfactories> <add name="dotconnect sqlite" invariant="devart.data.sqlite" description="devart dotconnect sqlite" type="devart.data.sqlite.sqliteproviderfactory, devart.data.sqlite, version=4.6.287.0, culture=neutral, publickeytoken=09af7300eec23701" /> </dbproviderfactories> </system.data> after add below block code in app.config <?xml version="1.0"?> <configuration>   <configsections> <!-- more information on entity framework configuration, visit http://go.microsoft.com/fwlink/?linkid=237468 --> <section name="entityframework" type="system.data.entity.internal.configfile.entityframeworksection, entit...
Read more

java - Copying object fields -

-
what best way of copying classes when need have 2 independent variables? have simple class: public class myclass { boolean = false; string b= "not empty"; } do need make method : assign(myclass data ) { a= data.a; b= data.b; } is there automatic method copy (duplicate) objects in java? do need make method : pretty close. instead of making method, should make constructor. such constructors called copy constructor , , create them this: myclass(myclass data) { = data.a; b = data.b; } and create copy of instance, use constructor this: myclass obj1 = new myclass(); myclass obj2 = new myclass(obj1); copy constructor can tedious : using copy constructor create deep-copy can tedious, when class has mutable fields. in case, assignment create copy of reference, , not object itself. have create copy of fields (if want deep copy). can go recursive. a better way create deep copy serialize , deserialize object. why not use clone()? ...
Read more

c++ - Clear the memory after returning a vector in a function -

-
i have function processes , stores lot of data in , returns results vector of class. amount of data stored in function tremendous , want clear storage memory of function after finished job. necessary (does function automatically clear memory) or should clear memory function? update: vector<customers> process(char* const *filename, vector<int> id) { vector<customers> list_of_customers; (perform actions) return list_of_customers; } variables defined locally within function automatically released @ end of function scope. destructors objects called, should free memory allocated objects (if objects coded correctly). example of such object std::vector . anything you've allocated new must have corresponding delete release storage. try avoid doing own allocation , use raii instead, i.e. containers or smart pointers.
Read more