Image Processing Reference
In-Depth Information
2.2 NR IQA Tools
2.2.1 Sharpness degree
by the following equation:
(3)
where
2.2.2 Blur metric
Another tool for measuring blur atempts to obtain the spread of the edges. First, an edge de-
tector (e.g., a Sobel edge detector) is applied to a grayscale image. We scan each row of the
image for pixels corresponding to an edge location. The start and end positions of the edge
are defined as the locations of the local extrema closest to the edge. The spread of the edge is
then given by the distance between the end and start positions and is identified as the local
blur measure for this edge location. The global blur measure for the whole image is obtained
(4)
2.2.3 Blind image quality index
quantiies this distortion using an NSS-based approach. Given a distorted image, the al-
gorithm first estimates the presence of a set of distortions in the image that consists of JPEG,
JPEG2000, white noise, Gaussian Blur, and Fast fading. The amount or probability of each dis-
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