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Asked: 2026-06-16T02:49:51+00:00

My question is – can I recognize different templates in a source image using

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My question is – can I recognize different templates in a source image using feature detection in OpenCV? Let’s say my templates are road signs.

I am using ORB, but this is not tracker-specific question.

My basic approach without feature detection is:

  • Image preparation (filtering etc);
  • Detecting ROI where my object may be located;
  • Resizing ROI to templates’ size and comparing with each template I have (ie. template matching);
  • Maximum correlation after comparison is an object I look for.

But with feature detection I detect keypoints and descriptors for each image in my template set and for my ROI where object might be located, but matcher returns distances for all descriptors I have in my ROI.

I can’t tie this to any correlation between ROI and templates, or, in other words, I can’t decide whether ROI image and template image are the same objects based on information provided by matcher.

So, to be more specific – is my approach wrong and feature detectors are used to detect one template object in a source image (which is not what I need) or I’m just not grasping the basic concepts of feature detection and thus am in need of help.

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1 Answer

  1. Editorial Team

    You may be missing two aspects. One is to remove outliers in your feature matching using a method like RANSAC+homography. The second point is to project the corners of your template to the scene, to make a “rectangle” of your image. Also you should define a threshold on how many inliers you will consider the minimum for a right detection.

    Check this tutorial on finding objects with feature detection.

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