new_uleft = uleft[0] + x1 / size[0] * xwidth, uleft[1] - y1 / size[1] * ywidth
new_lright = uleft[0] + x2 / size[0] * xwidth, uleft[1] - y2 / size[1] * ywidth
How to 'zoom' in on a section of the Mandelbrot set?