If you have to work with multiple images and you do routine work on each one of them, ReaConverter is the program you were looking for. It is a great tool for applying countless operations on multiple images.
This process only requires three steps:
1. Choose the group of images you want to work on.
2. Select the operations you want to carry out: conversion of image formats, watermarks, transparencies, effects …
3. Execute the operations and store all the results automatically in the desired directory.
The program can work with hundreds of different formats, including the advanced types RAW, EPS, AI, and PDF. It also allows you to work with command lines and even schedule conversion tasks.