SunlitGreen BatchBlitz is a powerful tool for processing an entire folder of digital images, all at the same time.
If your photo collection is just a disorganised mess, for instance, then you can have the program organise the shots into folders based on their EXIF or IPTC data. So you could, say, categorise your photos by the day they were taken, the rating you've given them, the camera that took them, whatever works for you.
Alternatively, you might rename a group to images to follow consistent rules, again including sequence numbers, image dimensions, EXIF data and more.
The program can also convert your set of images to a particular format (as long as it's PNG, JPG or BMP, anyway).
And most powerful of all, you can apply a set of image editing processors to your photos, that will change their content. So you're able to add an image or text-based watermark; automatically set the optimum contrast or colour levels; and crop, resize or rotate the image, amongst other operations.