Add function to cast Mat into io.Reader

[plutov]

When I use this code:

imgFace := img.Region(r)

Then to be able to get image data, I need to save into file using:

gocv.IMWrite(imgName, imgFace)

And then I can use os.Open and get io.Reader type. But I think it can be helpful to have this in gocv.

[deadprogram]

Hello, @plutov sounds like you might be looking for what the IMEncode() function already does:

https://godoc.org/gocv.io/x/gocv#IMEncode

[plutov]

Awesome, didn't see it.