5. Digital images often have to be rotated (for example, in response to a twist of the iPod Touch). The fundamental process is straightforward. Consider a single pixel at location (x,y). We would like to rotate it through an angle of Φ radians. Doing so is quite easy. We convert it to polar co-ordinates (r, Θ) add Φ to Θ and convert back to the new rectangular co-ordinates. This results in the following two expressions:
where and are the new (x,y) co-ordinates after rotation by Φ radians.
We want a function to compute a new value for x and y given an existing value and the desired rotation angle Φ.
(a) Create the header comment and the prototype for the function.
(b) Create the code for the function. (You may assume has been declared and may use any of its standard functions). Comments are not required; we won't be marking for style.