Use the Transform tab to select batch transformations (if required).
Typically the batch resize tool is used to make thumbnail images but you can also use it to reduce a batch of images to a maximum size.
If you specify just a Width or Height the other dimension will be scaled to keep the aspect ratio fixed.
If you specify Width and Height both dimensions will be scaled and the aspect ratio of the image will be lost.
Fit to box: both dimensions will be scaled so that the image will fit as closely as possible to the given dimensions but while still preserving the aspect ratio. This mode is useful for making thumbnail images to fit in a table.
Don’t Enlarge Image: will ensure that the image is never increased in size. This can be useful for limiting the size of a batch of images to maximum dimensions.
Background: Specifying a color will pad the image out with solid color so that it fills the dimensions given.
Rotate: The image can be rotated in 90 degree steps prior to the resize.