Smoothing and Sharpening
Digital images can be improved or altered for a special purpose by many processes including by smoothing or sharpening which seems contradictory.
Within any picture a few of the pixels will be“wrong”. There will be errors in the recording. For example this blue pixel is darker than the others around it. We can reduce these by smoothing.
The software examines the code of each pixel and makes each an average of those immediately around, like this:
Smoothing reduces these odd errors but will also remove other information from the image. Note that the edge between the blue and the head is softened and blurred.
Sharpening does the opposite to smoothing, enhancing the differences between adjacent pixels and increasing the contrast at boundaries between colours.