Creating a Nexus S Wallpaper

So you've got a snazzy Nexus S Android phone and you want to use one of your own photos as wallpaper? Well it certainly can be easy enough, open a picture using the Gallery application then from the menu choose More - Save As - Wallpaper. Drag the crop box around and resize it by touching a side if necessary and your picture becomes the wallpaper. But since only a vertical slice from the wallpaper is shown on screen maybe you couldn't select as precisely as you wanted and an important part of the picture isn't visible. Or maybe you want more control over the final image, like resizing it to the actual wallpaper dimensions.

The first thing you need to understand is that only a small region of the wallpaper is shown at any time. This is because there are five different "desktops" that can be scrolled side-to-side. As the user swipes their finger across the screen the other desktops are shown and the wallpaper image scrolls slightly along with the icons and widgets. Because of this the wallpaper image needs to be wide enough to cover all five of the desktops. It turns out that the final wallpaper size is 960 by 800 pixels. The screen size is 480 by 800, so with each finger swipe the image moves by 1/5.

The starting picture is a 3:2 aspect ratio image. It has been resized so that it is 1200 pixels wide by 800 pixels high.

Original 3:2 aspect ratio photo

The first thing is to determine what the center screen should look like.

Selection indicating the region that will be visible in the center desktop. Note that the selection is not centered in the picture.

Once that's done the final wall paper region can be defined by expanding the selection so that it's 960 pixels wide.

The final wallpaper 960 pixel wide selection

Finally crop the image and save it to your Nexus S. Use the Gallery application to view the image and choose the Wallpaper menu item; for some reason Google decided that the crop box will never select the whole image, so you'll need to move and resize it to select the whole picture. There you go, your own custom wallpaper.

The final wallpaper image.
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