I need to get the background model of a Mixture of Gaussian with opencv. I know that there is a method called getBackgroundImage in C++ I searched if it is possible to get it in python interface but I haven't get good result. I Tried opencv 3.0.0-dev because it has BackgroundSubtractorMOG2 implementation, but help() function don't document method implementation for background model. Do you know if there is undocumented implementation? I searched how to edit opencv source to implement a python implementation but i haven't found documentation about it. I prefer avoid to use scipy.weave to compile c++ code, furthermore i don't know if scipy.weave is useful in thi situation
Zaw Lin's solution in Ubuntu 12.04:
The main difference is that the result (fg
/ bg
) images are created/allocated in python and then passed down to the c++ lib.
Zaw Lin's solution was giving me errors (errno 139 - SIG_SEGV), because of the app was accessing invalid memory zones. Hope it saves someone a couple of hours :)
mog2.cpp:
#include <opencv2/opencv.hpp>
cv::BackgroundSubtractorMOG2 mog(100, 16, false);
extern "C" void getfg(int rows, int cols, unsigned char* imgData,
unsigned char *fgD) {
cv::Mat img(rows, cols, CV_8UC3, (void *) imgData);
cv::Mat fg(rows, cols, CV_8UC1, fgD);
mog(img, fg);
}
extern "C" void getbg(int rows, int cols, unsigned char *bgD) {
cv::Mat bg = cv::Mat(rows, cols, CV_8UC3, bgD);
mog.getBackgroundImage(bg);
}
Compile it like:
gcc -shared -o libmog2.so -fPIC ./mog2.cpp -lopencv_core -lopencv_highgui -lopencv_objdetect -lopencv_imgproc -lopencv_features2d -lopencv_ml -lopencv_calib3d -lopencv_contrib -lopencv_video
And then python:
mog2.py
import numpy as np
import ctypes as C
import cv2
libmog = C.cdll.LoadLibrary('path/to/libmog2.so')
def getfg(img):
(rows, cols) = (img.shape[0], img.shape[1])
res = np.zeros(dtype=np.uint8, shape=(rows, cols))
libmog.getfg(img.shape[0], img.shape[1],
img.ctypes.data_as(C.POINTER(C.c_ubyte)),
res.ctypes.data_as(C.POINTER(C.c_ubyte)))
return res
def getbg(img):
(rows, cols) = (img.shape[0], img.shape[1])
res = np.zeros(dtype=np.uint8, shape=(rows, cols, 3))
libmog.getbg(rows, cols, res.ctypes.data_as(C.POINTER(C.c_ubyte)))
return res
if __name__ == '__main__':
c = cv2.VideoCapture(0)
while 1:
_, f = c.read()
cv2.imshow('f', f)
cv2.imshow('fg', getfg(f))
cv2.imshow('bg', getbg(f))
if cv2.waitKey(1) == 27:
exit(0)
here's a simple wrapper using ctypes, i have only tested on windows
cpp, build as dll
#include "opencv2/opencv.hpp"
cv::BackgroundSubtractorMOG2 mog(100, 16, false);
cv::Mat bg;
cv::Mat fg;
extern "C" __declspec(dllexport) unsigned char* getfg(int rows,int cols, unsigned char* fdata)
{
cv::Mat frame= cv::Mat(rows, cols, CV_8UC3,fdata);
mog(frame,fg);
//check fg.iscont(), copy as needed
return fg.data;
}
extern "C" __declspec(dllexport) unsigned char* getbg()
{
mog.getBackgroundImage(bg);
return bg.data;
}
python
import cv2
import numpy as np
import ctypes as C
lib = C.cdll.LoadLibrary('wrapper.dll')
def getfg(img):
ptr = lib.getfg(img.shape[0],img.shape[1],img.ctypes.data_as(C.POINTER(C.c_ubyte)))
buf = (C.c_ubyte * img.shape[0] * img.shape[1] * 1).from_address(ptr)
res = np.ndarray(buffer=buf, dtype=np.uint8,
shape=(img.shape[0], img.shape[1], 1))
return res
def getbg(img):
ptr = lib.getbg()
buf = (C.c_ubyte * img.shape[0] * img.shape[1] * 3).from_address(ptr)
res = np.ndarray(buffer=buf, dtype=np.uint8,
shape=(img.shape[0], img.shape[1], 3))
return res
c = cv2.VideoCapture(0)
while(1):
_,f = c.read()
cv2.imshow('f',f)
cv2.imshow('fg',getfg(f))
cv2.imshow('bg',getbg(f))
if cv2.waitKey(1)==27:
exit(0)
opencv 3.0
bgd=dict(history=20,nmixtures=20,backgroundRatio=0.5,noiseSigma=0)
fgbg=cv2.bgsegm.createBackgroundSubtractorMOG(**bgd)
来源:https://stackoverflow.com/questions/19031836/get-background-model-from-backgroundsubtractormog2-in-python