title: Determining coordinates for mandelbrot zoom
body: <p>I got a mandelbrot set I want to zoom in. The mandelbrot is calculated around a center coordinate, mandelbrot size and a zoom-level. The original mandelbrot is centered around 
  real=-0.6 and im=0.4 with a size of 2 in both real and im.</p>
  
  <p>I want to be able to click on a point in the image and calculate a new one, zoomed in around that point</p>
  
  <p>The window containing it is 800x800px, so I figured this would make a click in the lower right corner be equal to a center of real=0.4 and im=-0.6, and a click in the upper left corner be real=-1.6 and im=1.4</p>
  
  <p>I calculated it with: <br>
  for the real values<br>
  800a+b=0.4 => a=0.0025<br>
  0a+b=-1.6 => b=-1.6<br></p>
  
  <p>for imaginary values<br>
  800c+d=-0.6 => c=-0.0025<br>
  0c+d=1.4 => d=1.4<br></p>
  
  <p>However, this does not work if I continue with mandelbrot size of 2 and zoom-level of 2. Am I missing something concerning the coordinates with the zoom-levels?</p>