OpenCV face recognition prediction and confidence values

asked 2017-09-27 05:34:26 -0600

Sagar9172
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Hi, i am developing face recognition software using OpenCV in C++. For that i am using createLBPHFaceRecognizer(). So when i call predict function(e.g. model->predict(face, predictedLabel, predictedConfidence)), i am getting confidence value around 100 when user face is near to camera but as i maintain some distance between camera and face then it will give confidence around 200 or max sometimes. So i am confused about this result. why i am getting this much of variation. Is there something i missed ? And which confidence is good, 100 or 200?

answered 2017-09-27 05:49:43 -0600

berak
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what you get as "confidence", is actually the opposite - the distance to the closest item in the database.

(so, 100 is better than 200, and 0 would be a "perfect match")

so, if you move away from the camera, the recognition will degrade.

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But if i give used 1.jpg for training and after that i used same image(1.jpg) in recognition as a input. Still is is giving confidence like 70-80. But according to all documents it should give 0. Isn't it?

Sagar9172 ( 2017-09-27 06:03:04 -0600 )edit

hard to see, what you're doing, but you probably should not use jpg images for this. lossy compression and the blocky compression artefacts seriously mess with the lbph algorithm

berak ( 2017-09-27 08:41:15 -0600 )edit

@berak then which img format should we use....& one more Q does img quality,size,resolution,scalefactor value.... increases the confidence value....

wasit ( 2019-06-08 06:28:36 -0600 )edit

@wasit, if you can, prefer png or similar.

but in 2019, you should probably use a facenet encoding, not lbph

berak ( 2019-06-08 07:47:17 -0600 )edit

@berak tnks...

wasit ( 2019-06-09 10:27:13 -0600 )edit

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