Color image smoothing and sharpening are spatial filtering techniques used to improve image quality by either removing noise (smoothing) or highlighting edges and details (sharpening).
Unlike simple pixel-wise transformations, these techniques use neighboring pixel information to modify each pixel’s value. In full-color images (e.g., RGB), each pixel is a vector with multiple components.
Color Image Smoothing
Definition:
Smoothing reduces image noise and softens fine details. It is done by averaging neighboring pixels.
Method:
We apply a spatial averaging filter (e.g., a box filter or mean filter) over a neighborhood around each pixel.
In grayscale images, smoothing is done as:

It follows from Eq. (6-37) and the properties of vector addition that



