Scale a bunch of images

I have a lot of images. The orientation of the images are not the same. A few of them are landscape format, the others portrait format.

Is it possible to scale down the portrait formated images to a fix height of 640px and scale down the landscape formated images to a fix width of 640px in one step?
At the moment I have to split the images in landscape format and portrait format and process them in two steps. It would be great if Phatch could recognize the orientation of the images and take care of the right output size.