fabrizio_m's profile - activity

My colleague has adapted it for HOG+SVM already, but I need to do it with KNN. :(

K-Nearest for handwritten letters I'm working with this data set, which Is slightly unbalanced across the letter classes

K-Nearest for handwritten letters I'm working with this data set, which Is slightly unbalanced across the letter classes

Nearest for handwritten letters I'm working with this data set, which Is slightly unbalanced across the letter classes:

Nearest for handwritten letters I'm working with this data set, which Is slightly unbalanced across the letter classes:

Nearest for handwritten letters I'm working with this data set, which Is slightly unbalanced across the letter classes:

Thanks a lot for testing this out. The input data is just getting passed into the code that calls opencv from a view controller in an iOS app that loads the input images from the device's filesystem. And then I return the results (result, regionmatchingTemplate Mat instances) back up for display to the user. Just curious, which platform did you test this on? I may switch to a different reference platform, as I've definitely had issues on iOS.

Hi all, I'm trying to subtract two Mat instances to obtain a result that represents a person's signature. Unfortunately, my resulting Mat seems to show noise along the top edge. Here are the source images and output:

The templateToMatch: C:\fakepath\template.png

The original source from which the ROI will be extracted, referred to as "formImage" in the code:C:\fakepath\sep-ira-completed-handwritten-p5.png

The ROI extracted via matchTemplate and Rect:C:\fakepath\signed.png

The result of running subtract on the template and extracted ROI: C:\fakepath\difference.png

As you can see, difference.png shows noise creeping down over the actual signature.

Can someone have a look at my implementation and tell me what I may be doing wrong? Is there a way I can mitigate this, if not avoid it altogether?

Here's where the subtraction takes place:

cv::Mat extractSignatureFromRegion(cv::Mat & templateToMatch, cv::Mat & formImage, bool* sigFound) {
    Mat signature;
    Mat result;
    bool hasSignature = false;
    Mat sigRegion = getSignatureRegion(templateToMatch, formImage);

    subtract(templateToMatch, sigRegion, signature);
    cvtColor(signature, signature, CV_BGR2GRAY);
    if (countNonZero(signature) > 0) {
        hasSignature = true;
    }
    *sigFound = hasSignature;
    return signature;
}

Here's the getSignatureRegion that uses template matching to extract the potentially signed region in the source doc:

    cv::Mat getSignatureRegion(cv::Mat & templateToMatch, cv::Mat & formImage) {
    //Create result matrix from template and original source
    Mat resultImg;
    Mat resultMatrix;
    Mat regionMatchingTemplate;
    Mat result;
    double minVal;
    double maxVal;
    Point minLoc;
    Point maxLoc;
    Point matchLoc;

    int resultColumns = formImage.cols - templateToMatch.cols + 1;
    int resultRows = formImage.rows - templateToMatch.rows + 1;
    resultMatrix.create(resultColumns, resultRows, CV_32FC1);


    // Match template and normalize
    matchTemplate(formImage, templateToMatch, resultMatrix, CV_TM_SQDIFF);
    normalize(resultMatrix, resultMatrix, 0, 1, NORM_MINMAX, -1, Mat());
    minMaxLoc(resultMatrix, &minVal, &maxVal, &minLoc, &maxLoc, Mat());
    matchLoc = minLoc;
    regionMatchingTemplate = formImage(Rect(matchLoc.x, matchLoc.y, templateToMatch.cols, templateToMatch.rows));
    regionMatchingTemplate.copyTo(result);
    return result;
}

Here's another example where this time, I used a template to extract a region from an empty form where no signature is present in the ROI. I would expect the subtract operation to result in a nearly empty Mat, but again there is "noise" along the bottom edge of the result:

Unsigned form: C:\fakepath\rollover-signature-page-unsigned.jpg

Template to find ROI of empty signature box: C:\fakepath\template.png

ROI that was extracted from unsigned form: C:\fakepath\signed.png

And finally, the subtract result with a weird black rectangled along bottom edge: C:\fakepath\difference.png