It depends on how much of the pipes are corroded.
Disassemble the connections and slide the fittings back along the pipe. If the pipe looks good and you just want to replace the connectors, you should be able to just cut off the flared ends, put new fittings on and re-flare. You will have lost very little of the pipe and they should fit back together.
If you need to cut back further, then you may need to cut out a longer section and use a couple of connectors to insert a new piece of pipe, or replace a full section of pipe all the way to the next joint.
You may find that after removing them from the bracket and giving them a clean they may not be as bad as they look. As long as there is no pitting in the pipe and the fittings are not heavily corroded, you should be fine. The pipe can corrode inside the fittings, so disassembling them and examining the pipe is a good idea.