Which app do I need for my iPad Pro?

Hi,

i have just purchased an iPad Pro as I was foolish enough to think it would replace my laptop! Anyway, I use photoshop elements on my mac and pc to make product images for our website. The functions I need are as follows;

1. Set a background layer in a size of my choice.

2. Make the background either transparent or white

3. Place a cropped image on top of it.

4. Save as either JPG or PNG24

Simple functions but I cannot find any app that does this. We need to make 500x500px images for our website, the hi-res images we use from our suppliers are sometimes an obscure size so we crop image to show just the product, cut it and paste onto a white background.

Can anyone suggest an app that I can use on this overpriced tablet to achieve this.

Thanks in advance.

Lee