Google made an amazing app called Snapseed that can be used to fix the perspective in your shots - after you have taken them. It's a free app.
Here is a quick demonstration of the magic Snapseed can do for you. This 1:55 video will show you how to get from the first to the second of the images below. Look at the difference in perspective. You can do this also.
If you want to learn more about Snapseed, just search for Snapseed tutorials on YouTube.
Note how the sides of this palace are leaning heavily inwards. They are nowhere near to parallel to the edge.
Now the building looks as if it was a straight shot taken from 7 meters up high. Snapseed fixed it. The brightness was also improved.
Before
After
Here Snapseed was used to rotate an image and fix the outwards leaning vertical lines. Which version do you think is best? Before or after?
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