[英]Passing OpenCV Image as function argument with ctypes
I have written some optimized C++ code for FLANN Matching with SIFT features (OpenCV) that returns the number of good matches ( int
) found on two images. 我已经为FLANN匹配SIFT功能(OpenCV)编写了一些优化的C ++代码,该代码返回在两个图像上找到的良好匹配数(
int
)。 My code works well when I pass the two image paths (query and train images) as char*
via ctypes
. 当我通过
ctypes
将两个图像路径(查询图像和训练图像)作为char*
传递时,我的代码运行良好。 I am writing a wrapper class in Python to handle these functions. 我正在用Python编写包装类来处理这些功能。 However, I want to pass the two arguments as image instances and not as
char*
or std::string
, namely the objects that are results of cv2.imread(apath)
in Python OpenCV bindings. 但是,我想将两个参数作为图像实例而不是
char*
或std::string
传递,即Python OpenCV绑定中cv2.imread(apath)
结果的对象。
My .cpp
source code: 我的
.cpp
源代码:
//detectors.cpp
#include <stdio.h>
#include <iostream>
#include "string.h"
#include "opencv2/core/core.hpp"
#include "opencv2/features2d/features2d.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/nonfree/features2d.hpp"
#include "opencv2/opencv.hpp"
using namespace cv;
using namespace std;
///* (extern c) Get good matches using SIFT and FLANN Matcher * ///
extern "C" int get_matches_sift_flann(char* img1, char* img2)
{
Mat img_1 = imread(img1, CV_LOAD_IMAGE_GRAYSCALE );
Mat img_2 = imread(img2, CV_LOAD_IMAGE_GRAYSCALE );
//-- Step 1: Detect the keypoints using SIFT Detector
int minHessian = 400;
SiftFeatureDetector detector( minHessian );
std::vector<KeyPoint> keypoints_1, keypoints_2;
detector.detect( img_1, keypoints_1 );
detector.detect( img_2, keypoints_2 );
//-- Step 2: Calculate descriptors (feature vectors)
SiftDescriptorExtractor extractor;
Mat descriptors_1, descriptors_2;
extractor.compute( img_1, keypoints_1, descriptors_1 );
extractor.compute( img_2, keypoints_2, descriptors_2 );
//-- Step 3: Matching descriptor vectors using FLANN matcher
FlannBasedMatcher matcher;
std::vector< DMatch > matches;
matcher.match( descriptors_1, descriptors_2, matches );
double max_dist = 0; double min_dist = 100;
//-- Quick calculation of max and min distances between keypoints
for( int i = 0; i < descriptors_1.rows; i++ )
{ double dist = matches[i].distance;
if( dist < min_dist ) min_dist = dist;
if( dist > max_dist ) max_dist = dist;
}
//-- Draw only "good" matches (i.e. whose distance is less than 2*min_dist,
//-- or a small arbitary value ( 0.02 ) in the event that min_dist is very
//-- small)
//-- PS.- radiusMatch can also be used here.
vector< DMatch > good_matches;
for( int i = 0; i < descriptors_1.rows; i++ )
{ if( matches[i].distance <= max(2*min_dist, 0.02) )
{ good_matches.push_back( matches[i]); }
}
int n = (int) good_matches.size();
return n;
}
And my python wrapper.py
module 还有我的python
wrapper.py
模块
#wrapper module for libdetectors.so
import os
import ctypes as c
libDETECTORS = c.cdll.LoadLibrary('./libdetectors.so')
class CExternalMatchesFunction:
def __init__(self, c_func):
self.c_func = c_func
self.c_func.argtypes = [c.c_char_p, c.c_char_p]
self.c_func.restype = c.c_int
def __call__(self, train_img_filename, query_img_filename):
r = self.c_func(c.c_char_p(train_img_filename), c.c_char_p(query_img_filename))
return r
#initialize wrapped functions
get_matches_sift_flann = CExternalMatchesFunction(libDETECTORS.get_matches_sift_flann)
All in all, I want to change CExternalMatchesFunction().c_func.argtypes
to a list of image objects like these: 总而言之,我想将
CExternalMatchesFunction().c_func.argtypes
更改为像这样的图像对象列表:
import cv2
img1 = cv2.imread('foo.jpg')
img2 = cv2.imread('boo.jpg')
Thanks in advance 提前致谢
解决方案:返回void*
并在通过时再次将其强制转换为cpp对象
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