Are there any apps that will sharpen the quality of pictures taken with the camera?

There are plenty. My favorite is Snapseed, which offers two different sharpening modes for different situations.

Be aware, though, that there's only so much you can do for a photo that had poor focus to start with. An unsharp mask filter is good for regaining crispness after resizing or resampling, by fooling the eye into seeing more resolution than the display actually supports, but it can't magically provide detail missing from the original image.

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