NFHS Girls softball
 

When a legal pitch hits the ground halfway to the plate and the catcher runs out and picks it up before it crosses the plate, is this an illegal pitch. The batter did not get the opportunity to swing at the pitch. In the umpires judgment the pitch would have crossed the plate if the catcher had not of picked it up.

Its catchers obstruction, not an illegal pitch. If the ball is still moving toward the plate, the batter must be given the opportunity to hit the ball. If the ball stops short of the plate, then the catcher or another player can get the ball.

If you visualize what you described, the catcher is literally hindering the batter from the ball and the pitcher has done nothing illegal, unless it was deliberately bounced.