Nevermind, I got it:
$rads = ($this->angle * pi() / 180.0);
$tx = $px - ($px * cos($rads)) + ($py * sin($rads));
$ty = $py - ($py * cos($rads)) - ($px * sin($rads));
This is a programming problem, but the math is what I need help with.
The PHP ImagickDraw API's rotate() method does not take a pivot point in the parameters, it assumes the origin (0,0).
What I need to figure out is what to pass to translate(x,y) and rotate(degrees) to make a rectangle rotate about a specified pivot point.
So say I have pivotX and pivotY, how could I get the translateX, translateY, and rotation?
Additionally, I would like to know the new resulting bounding box that would be required to encompass the entire rectangle, but it's not absolutely necessary.