Algorithm to rotate an image 90 degrees in place? (No extra memory)

Question

In an embedded C app, I have a large image that I\'d like to rotate by 90 degrees. Currently I use the well-known simple algorithm to do this. However, this algorithm requi

Answer 1

This might be too vague, and not be what you're looking for, but I'm gonna post anyway.

If you consider an image to be a 2d array of pixels, you only need to reverse the order of either the top-level or nested array, depending on whether you want horizontal or vertical flipping..

So you would either loop through each pixel column (0->columns/2), and swap them (so you only need temp memory for 1 pixel, not the whole picture), or loop through rows for horizontal flipping.. Does that make sense? Will elaborate / write code if not..