Why OpenCV matchTemplate API not detect all occurrence of image?

asked 2018-03-19 02:32:56 -0600

Kailash
31 ●1 ●3

updated 2018-03-21 09:45:33 -0600

I am not able detect all occurrence of template image from source image. Please look attache below file and code for the same.

source Image: C:\fakepath\source.JPG

Template Image: C:\fakepath\target.jpg

In the source image there are 3 occurrence of template but matchTemplate API give only two( first and third). The second occurrence not found with 0.98 threshold. I can found the second occurrence with 0.8 threshold.

Can you help me what the wrong with below code?

How detect with all 3 occurrence with 0.98 threshold?

    cv::Mat ref = cv::imread("source.JPG");
    cv::Mat tpl = cv::imread("template.jpg")

    cv::Mat gref, gtpl;
    cv::cvtColor(ref, gref, CV_BGR2GRAY);
    cv::cvtColor(tpl, gtpl, CV_BGR2GRAY);

    cv::Mat res(ref.rows - tpl.rows + 1, ref.cols - tpl.cols + 1, CV_32FC1);
    cv::matchTemplate(gref, gtpl, res, CV_TM_CCOEFF_NORMED);    

    double THRESHOLD = 0.98;

    while (true)
    {
        double minval, maxval;
        cv::Point minloc, maxloc;
        cv::minMaxLoc(res, &minval, &maxval, &minloc, &maxloc);

        if (maxval >= THRESHOLD)
        {
            cv::rectangle(ref,maxloc,cv::Point(maxloc.x + tpl.cols, maxloc.y + tpl.rows),CV_RGB(0, 255, 0), 2);
            cv::floodFill(res, maxloc, cv::Scalar(0), 0, cv::Scalar(.1), cv::Scalar(1.));               
        }
        else
            break;
    }

    cv::imshow("result", ref);
    cv::waitKey();

Thanks

Case 1- I am using method CV_TM_CCORR_NORMED, which is working fine with most of the examples. But not working in few. using match-percentage/threshold 99%. see below screen, finding folder img, but it also gives false images.

source img - C:\fakepath\Capture.PNG target img - C:\fakepath\target.png output - C:\fakepath\folderSearch.JPG

Case 2-

Not finding the target img if source img is 75% of original img. using CV_TM_CCORR_NORMED, img open mode is IMREAD_COLOR. code using same that i posted, threshold is 95%.

source img - C:\fakepath\inflow75.PNG target img - C:\fakepath\target.png

output - 20180321.2011 - C:\fakepath\BergersAlgo.PNG

I tried the recent code posted here. Target was not found, I attached the screen.

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answered 2018-03-19 03:24:39 -0600

LBerger
9317 ●2 ●20 ●88 http://www.traimaocv.fr

updated 2018-05-14 03:41:45 -0600

Ok there is a problem but I don't think it is in your code. I have already post a solution. Now CV_TM_CCOEFF_NORMED should give you, good results but I have some doubt. I normalise signal before matchTemplate : that's only difference with your code. It shouldn't be necessary with CV_TM_CCOEFF_NORMED but may be a bug ? If you read doc w and h for image T and I shouldn't be equal. Normalisation is done before match template then TM_CCORR_NORMED is the good flag ~~You can work in color to improve results~~

int main(void) { Mat img = imread("capture.png", IMREAD_COLOR); Mat pen = imread("folder.png", IMREAD_COLOR); Mat black(3, 3, CV_8UC1, Scalar(255)); Mat result; Mat penF, imgF; vector<Mat>imgPlane; vector<Mat>tplPlane; split(pen, tplPlane); split(img, imgPlane); for (int i = 0; i < min(tplPlane.size(), imgPlane.size()); i++) { Mat r; imgPlane[i].convertTo(imgF, CV_32F, 1,-mean(imgPlane[i])[0]); tplPlane[i].convertTo(penF, CV_32F,1, -mean(imgPlane[i])[0]); matchTemplate(imgF, penF, r, TM_CCORR_NORMED); if (result.empty()) result = (r.clone()); else result = result + (r); } imshow("result", result); double minf, maxf; minMaxLoc(result, &minf, &maxf); Mat plus = result > 0.99*maxf ;// why 0.92? try and test Mat mask; dilate(plus, mask, black); img = imread("capture.png", IMREAD_COLOR); img(Rect(pen.cols / 2, pen.rows / 2, plus.cols, plus.rows)).setTo(Vec3b(255, 0, 255), mask); imshow("plus", img); waitKey(0); return 0; }

~~Why thereshold is not equal for all pens : as your image is in jpeg may be compression change pen shape and you have three pens in board image~~

try with https://github.com/LaurentBerger/Colo...

Now there is some limitation in this method and I think it can be improved color image is a 2D quaternion image and to solve this problem using matchtemplate method : Sangwine, S. J. and Ell, T. A.,“Hypercomplex Fourier Transforms of Color Images” and example in COLOR IMAGE REGISTRATION AND TEMPLATE MATCHING USING QUATERNION PHASE CORRELATION

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I update the question at end, Pls suggest on Folder img search example.

Kailash ( 2018-03-19 08:53:27 -0600 )edit

try in color : check new answer

LBerger ( 2018-03-19 09:59:54 -0600 )edit

Thanks Laurent, One case I found in which target img not found. please find "Case 2", I posted in question block.

Kailash ( 2018-03-20 02:43:40 -0600 )edit

First one error it was not max but min for. second I think we must substract same mean values for template and image

LBerger ( 2018-03-20 09:32:20 -0600 )edit

I tried this code, also updates. Running on Case 2, but not able to find the target images. also cv::split function is crashing on using vector. I tried array, it is running fine. please suggest why it is crashing on split. below is code section, I changed -

    Mat imgPlane[3];

Mat tplPlane[3];

cv::split(pen, tplPlane);

cv::split(img, imgPlane);

Kailash ( 2018-03-20 10:00:40 -0600 )edit

"crashing on using vector" error message? opencv version ? platform?

LBerger ( 2018-03-20 10:42:21 -0600 )edit

crashing on using vector on this line (cv::split(pen, tplPlane);) If changed to Mat array, it works.

Error - Exception thrown at 0x0F289FD0 (opencv_core330.dll) in Automation.ImageAlgorithmEXE.exe: 0xC0000005: Access violation writing location 0x61532E75.

version - 3.3.0

platform - windows 10

Kailash ( 2018-03-21 00:17:01 -0600 )edit

I don't think there is a problem with split and vector<mat> : this old example use vector<mat> and split. If you can give a small program with same problem you can post a new question or an issue.

Automation.xxxx.exe Are you really use official opencv lib or an opencv wrapper?

You should update your code to opencv 3.4.1 (deep learning module,..)

LBerger ( 2018-03-21 02:35:08 -0600 )edit

Same error - Exception thrown at 0x02B00F73 (opencv_core341.dll) in Automation.ImageAlgorithmEXE.exe: 0xC0000005: Access violation writing location 0xFDFDFDFD

I upgraded to opencv 3.4.1. I am using opencv official code and compiled it myself for libs and dlls.

here is my code -

    Mat img = imread("D:\\train9\\Capture 150.PNG", IMREAD_COLOR);  
    Mat pen = imread("D:\\train9\\target2.png", IMREAD_COLOR);
    Mat black(3, 3, CV_8UC1, Scalar(255));
Mat result;
Mat penF, imgF;
std::vector<cv::Mat>imgPlane;
std::vector<cv::Mat>tplPlane;

cv::split(pen, tplPlane);   // <- **crashing**
cv::split(img, imgPlane);
for (int i = 0; i < max(3, 3); i++)
{
    Mat r;
    imgPlane[i].convertTo(imgF, CV_32F, 1, -mean(imgPlane[i])[0]);
    tplPlane[i].convertTo(penF, CV_32F, 1, -mean

Kailash ( 2018-03-21 06:41:42 -0600 )edit

Are you trying linking release lib in debug mode?

LBerger ( 2018-03-21 07:57:13 -0600 )edit

yes I am linking release lib in debug.

Kailash ( 2018-03-21 08:49:44 -0600 )edit

Don't mix release and debug and crash should vanish

LBerger ( 2018-03-21 08:52:16 -0600 )edit

output - 20180321.2011 - C:\fakepath\BergersAlgo.PNG

I tried the recent code posted here. Target was not found, I attached the screen. Please suggest.

Kailash ( 2018-03-21 09:45:53 -0600 )edit

Thanks Laurent, it is working on given image. But on some images its not working, in which earlier working. I can share those images with you. Please share email or storage for sharing.

Kailash ( 2018-03-22 02:04:32 -0600 )edit

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