[英]Different template matching result in OpenCV and Matlab
I do template matching in MATLAB and C++ using OpenCV with two sample image and I get different results. 我使用带有两个示例图像的OpenCV在MATLAB和C ++中进行模板匹配,但得到了不同的结果。
My sample images are: 我的示例图像是:
crop 作物
temp 温度
when I use: 当我使用时:
Mat crop = imread("crop.jpg",0),
temp = imread("temp.jpg",0);
int resultWidth = crop.cols-temp.cols + 1;
int resultHeigth = crop.rows -temp.rows + 1;
Mat result = cvCreateImage(cvSize(resultWidth ,resultHeigth),32,1);
matchTemplate(crop,temp,result ,CV_TM_CCORR_NORMED);
double minval, maxval;
CvPoint minloc, maxloc;
cvMinMaxLoc(&(IplImage)result ,&minval,&maxval,&minloc,&maxloc,NULL);
maxvalue
value is 0.93058246374130249
. maxvalue
值为0.93058246374130249
。
In Matlab: 在Matlab中:
temp = rgb2gray(imread('temp.jpg'));
crop = rgb2gray(imread('crop.jpg'));
tempMat = normxcorr2(tmep,crop);
[res,index] = max(max(abs(tempMat)));
And at this case, answer was 0.5753
. 在这种情况下,答案为
0.5753
。
Why the maximum value of the normalized cross-correlation is different? 为什么归一化互相关的最大值不同?
In order to make it work, I used as reference image this: 为了使其工作,我使用了以下参考图像:
and as template this: 并作为模板:
This is the (correct) OpenCV code to use: 这是要使用的(正确)OpenCV代码:
#include <opencv2\opencv.hpp>
using namespace cv;
int main()
{
Mat1b img = imread("path_to_image", IMREAD_GRAYSCALE);
Mat1b templ = imread("path_to_template", IMREAD_GRAYSCALE);
// Compute match
Mat result;
matchTemplate(img, templ, result, TM_CCORR_NORMED);
// Get best match
Point maxLoc;
double maxVal;
minMaxLoc(result, NULL, &maxVal, NULL, &maxLoc);
// Display result
Mat3b res;
cvtColor(img, res, COLOR_GRAY2BGR);
rectangle(res, Rect(maxLoc.x, maxLoc.y, templ.cols, templ.rows), Scalar(0, 255, 0));
imshow("Match", res);
waitKey();
return 0;
}
that produces this result: 产生以下结果:
This is the (correct) Matlab code to use: 这是要使用的(正确)Matlab代码:
temp = rgb2gray(imread('path_to_template'));
img = rgb2gray(imread('path_to_image'));
% Perform cross-correlation
c = normxcorr2(temp,img);
% Find peak in cross-correlation
[ypeak, xpeak] = find(c==max(c(:)));
% Account for the padding that normxcorr2 adds
yoffSet = ypeak-size(temp,1);
xoffSet = xpeak-size(temp,2);
% Displat matched area
hFig = figure;
hAx = axes;
imshow(img,'Parent', hAx);
imrect(hAx, [xoffSet, yoffSet, size(temp,2), size(temp,1)]);
that produces this result: 产生以下结果:
As you can see, the results are equivalent. 如您所见,结果是等效的。 The actual maximum number in the match result matrix is:
匹配结果矩阵中的实际最大数量为:
OpenCV: 0.99999815225601196
Matlab: 0.999988754172261
which we can consider as equal. 我们可以认为是平等的。 The small difference is probably due to minor differences in the internal implementation, but is not relevant.
细微的差异可能是由于内部实施中的细微差异,但并不相关。
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