Salt-and-pepper noise
Salt-and-pepper noise, also known as impulse noise, is a form of noise sometimes seen on digital images. For black-and-white or grayscale images, is presents as sparsely occurring white and black pixels, giving the appearance of an image sprinkled with salt and pepper.
Cause
Salt-and-pepper noise can be caused by sharp and sudden disturbances in the image signal. These may be from transmission errors, corrupted pixel elements in the camera sensors, or faulty memory locations in the storage media.
Removal
An effective noise reduction method for this type of noise is a median filter or a morphological filter. For reducing either salt noise or pepper noise, but not both, a contraharmonic mean filter can be effective.
Linear filters are generally ineffective for removing impulse noise.