Preset Lightbox image sizes

Does anyone know how to set lightbox/collection list images to a preset sizes so that when you upload images that are in defferent sizes it automatically resizes them to fit in the boxes and show as same size as all images?

Here is an example of images that messed up completely due to different image sizes:

And here is how i want it to look:

@Alexander_Grann - Use an aspect ratio and set the image to cover.