From the Store description:
Reduce image size or crop, shrink, resize, compress images in JPEG|PNG format to the exact pixels, percentage or proportion you specify for posting them on Facebook, Twitter, Pinterest, Reddit, Tumblr or any other social media to meet their size requirement.
- gives your digital images the perfect size and configuration to suit a wide range of applications. Whether it’s for a social media profile, product photo for your online store, or an e-newsletter, fast and easy image resizing makes your life easier.
- comes with Batch feature where you can resize/compress multiple images at once and can share resized/compressed pictures from the app.
- helps you reduce picture size keeping the best quality.
Here's the app in action on my Lumia 950 XL:
Slightly confusingly, the right side of the interface remains greyed and 'broken', though as you'll see, this is all filled in after the batch compress or resize....
In this case, resizing in progress - it's very quick, taking only a couple of seconds for five 8MP photos here.
You do get an interstitial add for another of the developer's apps - but this can be forgiven for a free tool, I think.
After resizing - with resolution and byte size reduction highlighted in grey - very impressive.
Tapping through to share or print a resized image (they also appear in Photos, of course, as usual), there are more links for the dev's other applications. Hey ho, why not!
You can grab this in the Store here. It's free, with just the shown ads and prompts to grab other apps from the developer. Worth keeping installed for that 'batch' occasion when you can't face manually resizing a set of 40 wedding photos?
(Discovered through MyAppFree)