Yes there are a couple of ways to achieve this:
1. You can start with a Blank Canvas from the Start tab. This doesn’t change an existing photo to white but lets you start from scratch with a white photo.
2. If already on a photo, you can use the Effects tab > Sketch tool (towards the end of the list but you can search for it at the top of the list) to paint a flat color over your entire photo. Note that you can increase the brush size really large to make this a fast job.
Let us know if you have any other questions.
Regards – The Ribbet Team