What program to use to change the size of a heap of raktinok?

Question

Image processing

There are about 1000 paintings of various sizes, divided into folders. 2-3 nesting levels. You need a Bulk Image Editor that can make all the pictures square by filling in the missing space with a white background.
There are a lot of similar programs, but they all work with a fixed image size. Tell me if anyone knows.

Answer 1

image fast stone resizer

Answer 2

faststone photo resizer - there you can not only change the size, but also set quality and watermarks and a whole lot more. and all this can be done in batches.