Hi.
I'm using OpenCV4Android to try out template matching on an android phone. Essentially what I'm doing is taking a picture of some object that I wish to detect, cropping it and saving it as a template.
I then use my android camera and a surface view to constantly get images from the camera. I am then applying template matching on each image, converting the image to a Mat first. However, when applying template matching I only get around 3-4 fps.
What I am essentially doing is this:
** mCameraMat = inputFrame.rgba();
int matchMethod = Imgproc.TM_CCOEFF_NORMED;
// mTemplateMat resized in terms of video size in prepareMediaRecorder.
// Very hacky solution so need to fix it!
int result_cols = mCameraMat.cols() - mTemplateMat.cols() + 1;
int result_rows = mCameraMat.rows() - mTemplateMat.rows() + 1;
mResult = new Mat(result_rows, result_cols, CvType.CV_32F);
// Move this to a new thread.
Imgproc.matchTemplate(mCameraMat, mTemplateMat, mResult, matchMethod);
Core.normalize(mResult, mResult, 0, 1, Core.NORM_MINMAX, -1, new Mat());
// Localizing the best match with minMaxLoc
MinMaxLocResult mmr = Core.minMaxLoc(mResult);
Point matchLoc;
if (matchMethod == Imgproc.TM_SQDIFF || matchMethod == Imgproc.TM_SQDIFF_NORMED) {
matchLoc = mmr.minLoc;
} else {
matchLoc = mmr.maxLoc;
}
// Draw a boundary around the detected object.
Imgproc.rectangle(mCameraMat, matchLoc, new Point(matchLoc.x + mTemplateMat.cols(),
matchLoc.y + mTemplateMat.rows()), new Scalar(TrackingActivity.r, TrackingActivity.g,
TrackingActivity.b, TrackingActivity.a), 2);
**
Where mTemplateMat is the template bitmap image converted into a Mat object.
The bottleneck is on the line
Imgproc.matchTemplate(mCameraMat, mTemplateMat, mResult, matchMethod);
If I remove that line, I get around 25 fps, which is much more acceptable. I'd be fine with anything above 13-14. I understand that template matching is a very expensive process and doing it every frame can be costly. I have tried to do it every 20 frames, but it still slows down the processing considerably, and the end video looks worse as there is a constant transition from a smooth fps display to a low fps display.
What are my options in optimising matchTemplate? Any tips are much appreciated.
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