How do i find the angle of rotation of an image's text with respect to its dimensions?

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I have an image which is horizontal. I can rotate the image by 90 degrees get the image in the proper orientation and can do further processing from there. How do I automate this as I am not always going to be sure how much rotation is required. I want the image to be in a vertical format where text go from left to right, like this web page.

How do I achieve this in python?