1.3.3 Filters to Reduce Noise and
Distortion, or to Enhance
- Histogram Level Adjustment, for brightness and contrast - can be linear or piece wise linear (which
includes thresholding)
- Sharpen - accentuates the edges in the image by finding the
edges and increasing the contrast between all adjacent pixels
- Sharpen Edge - sharpens only the edges of an image by finding
significant color or contrast changes and sharpening only those
- Unsharp mask - creates the illusion of increased focus by
producing a lighter and darker line on each side of an edge. When using
this filter, the user specifies the pixel parameters to determine the
final sharpening effect. This is useful for refocusing an image which
has become blurry from repeated scanning or other interpolation.
- Frame averaging - when the image taking system has a
relatively high level of random noise, another technique for noise is reduction is
to take many images of the exact same scene and average them. Take care to
avoid overflow before dividing by the number of images by using a sufficiently
large accumulation integer type.
