[discussion] What is the Way to measure Similarity between images-

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Hi,

I studying OpenCV library for a few months now. And I encountered different ways to solve this problem (find an Image from a array of images)

I aware that the semantics is important. example:

1. Find an image from DB of images that similar - use Img_Hash.
2. Find an image from DB of images that Not similar - use Histogram.

Also, I see people advised to use features. (Its not the formal usecase to my understanding..)

Will be happy to hear opinions from any kind..

p.s : It's for general knowledge purposes..