The sharpen filter can help bring into focus a blurry image by
increasing the contrast of adjacent pixels. Sharpen focuses a selection
and improves its clarity.
Sharpen intensity is adjusted using the scroll bar, The range of change
is from 0% to 100%. If the flag Lock alpha is enabled the
mask of transparency doesn't vary, i.e. the transparent pixels that
have opaque neighbours remain transparent.
The effect is applied to the image as you move the scroll bars and
you can see the effect in the
edit area and panel of properties
of the object. Press Apply button to make your changes
permanent.