You’d think choosing a photo to use on your iPhone lockscreen would be a pretty simple task. Scroll through your Camera Roll, choose a photo you like, hit Set and you’re done.

The reality is a little different. Half the time the photo you really want to use is landscape format (horizontal) and you need a vertical image. The iPhone will automatically crop it, and allow you to slide the image around to get a crop you like, but the result rarely does justice to the original shot.

The other half of the time, you find a portrait (vertical) photo which looks great on its own but then clashes with the clock and slide to unlock text when you set it as your lockscreen. Lockscreen Wallpaper Designer is a very simple app that aims to solve these problems … 

What the app does is take your chosen photo and then set it into a circular, rectangular or star-shaped aperture. It then uses the colors present in the photo to create a blurred surround that sets off the clock and slide to unlock message clearly and without over-writing the photo itself.

Let’s look at a few examples. Here’s a portrait shot I took in Sydney that I really like on its own but which looks terrible on a lockscreen, with the white clock against the white background:

And here’s the result after choosing a landscape crop in the app:

Landscape format photos are no problem: just select the rectangular aperture. Here’s my favourite shot from Shanghai where I’ve picked the best crop the Settings app allows:

Which again looks absolutely terrible. And here’s the same photo as processed by the app:

The app couldn’t be simpler to use. Open it, touch Change Image and select the photo you want to use from your Camera Roll (or any other album on your iPhone). Touch the aperture shape you want. Touch the photo to slide it horizontally and vertically to get the crop you want. Touch Save.

The app can’t set a lockscreen photo itself, so it instead saves the resulting wallpaper to your camera roll.

You then use Settings in the usual way: Wallpapers & Brightness > Choose a New Wallpaper > Camera Roll. Select the image the app just created, and there’s your new lockscreen.

I found that it was trivial to find photos that worked, and was especially pleased to be able to use landscape photos without losing most of the image. The blur surround the app creates is sympathetic to the photos, and I found myself consistently pleased with the results. It’s how I expect to create all my lockscreen photos from now on.

The app costs just 99 cents and is available on iTunes.