ricardo.nascimento's profile - activity

Hi!

I'm using hog_pedestrians.xml and haar_fullbody.xml files provided by OpenCV to detect human body. As I don't know any information about these XML files, is there a way I can calculate the hit rate / miss rate of my algorithm using these XML files?

I'm trying to find the distance to an object with my Android.

I know the real size of object, also done some camera calibration with OpenCV to calculate focal length, camera matrix and distortion parameters as well. To easy up the question, it's assumed that the orientation is 0 degrees (can compute the angle of the android device when detecting the object)

My previous method was using some sort of manual calibration: - Calculated the area in pixels at several known distances and saved both values (area and distance). Every time I see the object i compute a regression based on the area measured. But this method is obviously inaccurate.

So based in the parameters I know that I mentioned above, what do you recommend as best method?

Hi ! I have implemented an algorithm that detects several QR Codes using OpenCV for Android. I now would like to know the distance between my camera and the QR Code. I believe this can actually be done since I know the size of the code in the image, I also know the vertices points of three markers I identified. Anyone can recomend some reading on this subject?

Thanks

Hi,

If I know my target (QR Code on the ceiling) and the target X,Y,Z coordinates in the real world could I possibilly know my Android Camera coordinates? If I know what height is the camera and the orientation. I woud like to calculate the positioning of the camera related to the point right under the code. Can somebody recomend some lecture about this subject please?

I'm currently developing a project in Android Studio and I need to use some OpenCV libraries.

I know that Android Studio currently doesn't support NDK development but when doing my research i found that there are ways to manage things around.

I followed this tutorial to add opencv libraries to my project:

http://stackoverflow.com/questions/17767557/how-to-use-opencv-in-android-studio-using-gradle-build-tool/22427267#22427267

Everything worked fine but when I tried to test an OpenCV example like "FaceDetection" by doing this:

"Go to OpenCV Android SDK, pick a sample project that you’d like to try out.

First, delete the ‘res’ folder inside your own project app/src/main, then place the res folder from the samples inside your app/src/main folder.

First, delete the ‘java’ folder from app/src/main, then copy the ‘src’ folder from the samples in there (note, the src has to be renamed to java).

If you building example with native C++ files, you need to have NDK installed. Download it from Google’s developers portal, and add this line to your local.properties in the top-level of your project, below the sdk.dir line: ndk.dir=/path/to/your/android-ndk Build and run the example!"

I got these errors:

java.lang.UnsatisfiedLinkError: Couldn't load detection_based_tracker from loader dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/com.example.ricardonascimento.opencvexamples-2.apk"],nativeLibraryDirectories=[/data/app-lib/com.example.ricardonascimento.opencvexamples-2, /vendor/lib, /system/lib]]]: findLibrary returned null at java.lang.Runtime.loadLibrary(Runtime.java:358) at java.lang.System.loadLibrary(System.java:526)

the problem is when loading library

// Load native library after(!) OpenCV initialization

System.loadLibrary("detection_based_tracker");

What do you suggest to solve this problem? I have searched all over the web but didnt find anything.

Thanks in advance for helping!