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Should You Rather Crop or Mask Reference Images for Image Recognition?

Last Updated: Jun 11, 2018

Why is it important for image recognition to eliminate unnecessary elements?

Good reference images are crucial to boost your image recognition performance and keep your users happy.

One of the most important things to do is making sure that your reference images don’t contain unnecessary elements of the background that won’t be there or won’t look the same in real life.

image-recognition-painted-door-original-587940-edited.jpg

By eliminating distracting elements from your reference images that are not important for the experience – in this case, for instance, for a street art tour app – you make the recognition faster and more accurate, by focusing only on what’s important.

Why is it better to crop the image instead of using ‘masks’?

You might be tempted to start ‘masking’ or start photoshopping your heart out to get rid of those unnecessary details in the background.

However, as a rule of thumb, cropping the image is actually a better solution. See what we mean by using the example of the same painted door.

Image-Recognition-Masking.jpg

Masking the unnecessary or ‘changing’ elements of the background
is not a very good idea, because a huge part of the image area is ‘wasted’,
and the white squares may still make the matching with the real scene difficult.

In general, the more image area is devoted to the unique pattern, the better for the recognition.

Image-Recognition-Cropping.jpg

Cropping the photo so that the reference image only contains the part that is
relevant for the recognition is a better option.

What about recognition of other types of objects, such as a photo in a magazine?

In this article, we mainly addressed the recognition of everyday objects and scenes.

Similarly, if you want to recognize an object such as bottle, cropping the reference image so that it only includes the area with the unique pattern – typically, the label – is a better option than using the photo of the whole bottle.

Pretty much the same logics apply to the recognition of photos or print images, too. If you want to scan a photo in a magazine or some graphic illustration in a textbook, you should rather use a cropped photo file or a selected part of the page than using the whole page as the reference image.

Photo credit: Travellingclaus.com

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