This actually looks surprisingly straightforward for what the function is doing ...

This actually looks surprisingly straightforward for what the function is doing - certainly if you have domain context of image editing or document placement. You'll find it in a lot of UI code - this one uses bit shifts for efficiency but what it's doing is pretty straightforward.

For clarity and to demonstrate, this is basically what this function is doing, but in css:

.container {

  position: relative;

}

.obj {

  position: absolute;

  left: 50%;

  top: 50%;

  transform: translate(-50%, -50%);


}