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Recognize play card

October 4, 2013 - 8:15am #10

Hello, I want to implement an application for Android able to recognize play cards. In particular, my problem is that cards are arranged as here. So, I guess that the best way to recognize them is trying to read the number/letter (and symbol for the joker) on the corner, since I do not care about the suit of the cards. How can I do that? Sorry, but I am not an expert so please I need of your help.

Recognize play card

October 4, 2013 - 8:41am #9

At present, Vuforia does not allow recognizing a single letter (such as J, Q, K of the cards) or a single number.

If the occluded part of the cards is not too large, you could try recognizing each card as an Image target; however, from the picture you sent, it seems that most of the surface of each card would be typically covered by another card,....so this looks a challenging scenario.


Recognize play card

October 4, 2013 - 9:03am #8

Ok. But, what about to recognize letters and numbers as images? Because what I want to get is counting how many cards there are for each number/letter.

For instance, looking the previous example the first player has six Ks, one 7, five 8s, one 9, three Js and one joker. 

Recognize play card

October 4, 2013 - 11:45am #7

You could try, but the risk is that the letters / numbers, when handled as images, would result in a very low amount of details; i.e. the resulting image targets would likely have a low tracking rating;

see here for more details:



Of course, the best is to make a little test by generating one image target from one of those letters or numbers, and see what it gives.



Recognize play card

October 5, 2013 - 4:28am #6

I think you are right, but I want to follow your suggestion and make an attempt.

I was tryng to upload an image by the Target Manager and it asks to insert the image width, how can I choose the right value of that parameter?

PS: I know that Vuforia is designed to support AR, but what I need it is different. In fact, the scenario is:

  • User shots a photo
  • application counts play cards given the photo
  • application shows the number for each card

Can I do that?

Recognize play card

October 5, 2013 - 8:35am #5

The width is an arbitrary value. It's used to define the unit scale of the coordinate system used for tracking. So you can use the real width of the card, or define your own unit. But it's best to use values above 2 to avoid falling below the near clipping plane of the camera fustrum.

As Ale has stated, your application is going to be a challenge because the cards don't present many detectable features. Theoretically it's possible, if the targets are detectable. But you'll need to experiment to see if the cards you are using can be detected.

Recognize play card

October 5, 2013 - 8:55am #4

Ok, I will set as parameter the width of the card.

I uploaded some images which got 2 or 3 stars. Maybe, if I edit the images I can get some star more. 

Now, I do not have an Android phone with me, so I can not test it. Is there another way to do that?

Recognize play card

October 5, 2013 - 12:40pm #3

You can get a free 30 day trial of Unity Pro, which supports our simulator - https://developer.vuforia.com/resources/tutorials/vuforia-play-mode-unity

If you're able to edit the cards, then yes you'll be able to improve their ratings. Keep in mind how the user will be arranging them. For example, if they'll be stacked, you'll want to add features at the edges and corners that will be visible.

Recognize play card

October 6, 2013 - 5:27am #2

Thanks, I will test it by using your simulator.

Sorry, I meant that I could improve the rating by editing the image, I saw some tricks in your resources like increasing image contrast.

Recognize play card

October 6, 2013 - 8:24am #1

Local contrast enhancement will help a bit, but don't expect a dramatic improvement.

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