I need to know that different between scanning and taking photo from camera . As example we normally , SCAN QR code , bar code , like thing using android phone.They are also image. we can take photo from camera. it also image.
So ,is it Scanning QR code , mean take image and processing it or are there have any special thing take image from pixel values ?
Biggest difference is that when you capture an image you get a processed jpg file, when you're scanning you're working with raw YUV byte array.
When talking about a picture you usually need to worry about quality, flash, aperture, shutter speed, iso, white balance and a lot of other things that will make it a good picture and nice for people to see, and when you're working with a scan you usually don't care much about any of these things, you just need to get information from the image.
Another big difference is that you can capture a lot of YUV bytes very fast, while taking a picture takes time.
That covers the basic differences, but there's a lot of info when talking about photo and scanning, and more when you enter a specific subject. I suggest you to read about Camera and Camera preview.