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Visvalingam–Whyatt Algorithm
The Visvalingam–Whyatt algorithm, also known as the Visvalingam's algorithm, is an algorithm that decimates a curve composed of line segments to a similar curve with fewer points. Idea Given a polygonal chain (often called a Polyline), the algorithm attempts to find a similar chain composed of fewer points. Points are assigned an importance based on local conditions, and points are removed from the least important to most important. In Visvalingam's algorithm, the importance is related to the triangular area added by each point. Algorithm Given a chain of 2d points \left\ = \left\, the importance of each interior point is computed by finding the area of the triangle formed by it and its immediate neighbors. This can be done quickly using a matrix determinant. Alternatively, the equivalent formula below can be used : A_i = \frac \left, x_ y_ + x_i y_ + x_ y_ - x_ y_ - x_i y_ - x_ y_i \ The minimum importance point p_i is located and marked for removal (note that A_ and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decimation (signal Processing)
In digital signal processing, downsampling, compression, and decimation are terms associated with the process of ''resampling'' in a multi-rate digital signal processing system. Both ''downsampling'' and ''decimation'' can be synonymous with ''compression'', or they can describe an entire process of bandwidth reduction (filtering) and sample-rate reduction. When the process is performed on a sequence of samples of a ''signal'' or a continuous function, it produces an approximation of the sequence that would have been obtained by sampling the signal at a lower rate (or density, as in the case of a photograph). ''Decimation'' is a term that historically means the '' removal of every tenth one''. But in signal processing, ''decimation by a factor of 10'' actually means ''keeping'' only every tenth sample. This factor multiplies the sampling interval or, equivalently, divides the sampling rate. For example, if compact disc audio at 44,100 samples/second is ''decimated'' by a factor of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
