How to use "courtesy"?

English as a Second Language English Vocabulary, Grammar and Idioms
1

Please give me some examples.

2

There are many examples HERE. It would be useful for you to learn to use such websites.

3

We normally say to show courtsey.

e.g. He showed the lady courtesy by opening the door for her.

Rob
<wink … shiver!>

4

How to say express “The picture is provided by XXX” by using "courtesy?

I saw denotions as:

Picture courtesy of XXX.
Picture by courtesy of XXX.
Picture is courtesy of XXX( not sure this is correct or not).

5

Picture courtesy of XXX.
Picture by courtesy of XXX.
Picture is courtesy of XXX

As captions, these are all fine. Photo captions are often shortened in various ways.