The Photo Resize app offers two resize methods to make your product photos the same aspect ratio. Both have their benefits - so the choice between these two options really depends on your store design and your original images’ composition:
Cropping results in images resized to the selected aspect ratio, focusing entirely on the product.
Adding frames or borders maintain the original image size so you don’t lose any parts of your original content.
However, if you want to customize your resizing in terms of image dimensions and border size, we have another app that will be able to achieve what you're after - the Pixc: Image Editing app.
You can submit images from within your store
The app edits them and apply a template so that the images are all the same size and the products occupy the same space in the images.
Once your image is ready, you can replace them directly in your store.
Go ahead and give it a go - you will get 5 free images when you install the app.