Why am I getting incorrect match results?

If you are surprised that MobileEngine doesn’t return a correct match (or any match) for your query, the most common reasons are:

The reference image you expect to find is missing from your collection. To verify this, find the expected match in your collection if you know the filepath. 

If you don’t know the filepath, perform a search with a high quality query image of the same item (i.e. evenly lit, straight-on, tightly cropped). 

If your search still produces no matches, or incorrect matches, the correct reference image may not be in your collection, or it is poor quality (see below).

Your reference image is poor quality. If your reference image is too small, it may not be returned as a match. You can check the resolution of your images with the get_info endpoint. If you have photos of similar items, such as card or comic variants, your variant images may be larger, better lit, sharper, etc., making them better matches than the match you were expecting. 

Your query is poor quality. If you are just getting started with MobileEngine, make sure that you are not cropping part of the target image before uploading it. You may be cropping your images by accident, rather than scaling them to the recommended 600px minimum dimension. 

Otherwise, the most common example of a poor quality query is one where the subject is too small in the frame. Since your query images are scaled to 600 pixels in their smallest dimension, if the target object only takes up a fraction of the frame then it may be too small for MobileEngine to match correctly. You should encourage your users to take photos where the target takes up most of the frame and is in the same orientation as your reference images. An on-screen visual guide in your mobile application is helpful for this.

You can use the overlay returned by the search endpoint to confirm that the image received by MobileEngine matches the image you intended to send.

The feature you are trying to match is too small. If the only difference between variants of your item is a small symbol or text difference, then other factors like image skewness, lighting, and cropping may have a larger impact and cause similar variants to rank higher. 

Unless your reference images have very consistent quality, you should show all top matches with similar scores for your user to select from.

If you have challenges getting your query images to match, please reach out to us as we can provide specific feedback, and in some cases we can tune your deployment to work better with specific conditions.