Showing papers on "Run-length encoding published in 1985"

Data compression using run length encoding and statistical encoding

Abstract: A compression device which uses both run length encoding and statistical encoding. The run length encoding scheme uses a flag byte symbol which is disposed between a character signal and a run length symbol. The statistical encoding process uses multiple statistical encoding tables which are selected based upon previously occurring data.

Rearranging data to maximize the efficiency of compression

Abstract: We are concerned with rearranging the order in which data is stored in a database so as to maximize the amount of compression. We consider multi-attribute data defined over finite discrete domains (called categories ) and seek an optimal permutation of the categories for each attribute. We study both deterministic and probabilistic models of data distribution. We show that the deterministic category rearrangement problem is NP-complete (for run length encoding compression methods) via a reduction to the rectilinear traveling salesman problem. For the probabilistic model, we show that the optimal category rearrangement for each attribute has the form of a double pipe organ , which is a generalized version of the well-known pipe organ arrangement found in earlier work on record placement on disk cylinders. For k -dimensional data we obtain an algorithm for finding the optimal arrangement which is O ( n 2 ) for fixed k .

A hybrid image compression technique

Abstract: Many bandwidth compression techniques which have been applied to imagery can be characterized as low pass filters. Higher compression rates yield images with reduced resolution or sharpness. In general, the sharpness in an image is a function of high contrast edges. Several studies have shown that, although the presence of these edges is important to the overall subjective quality of the image, their fidelity is not. High contrast edge information can be isolated in the upper bit plane (the most significant bit) of most types of imagery. Simple run length encoding of this bit plane can be used to preserve the location and approximate peak amplitude of the edge information at an overhead cost of less than 0.1 bit/pixel. When upper bit plane run length encoding is combined with standard transform or DPCM coding: the resultant hybrid technique provides images with subjective quality improvements of better than two to one. This hybrid approach has been demonstrated on several types of imagery. Current activity is centered on an automatic intensity remapping function which guarantees the upper bit plane contains the optimal amount of information to ensure maximum run length encoding efficiency.

The Relationship between Euclid’s Algorithms and Run-Length Encoding

Abstract: The sequence of plotter moves generated by Bresenham’s algorithm for a single straight line can be expressed recursively as a sequence of repeated patterns A similar pattern can be seen in the flow of Euclid’s algorithm if it is applied to find the highest common factor of the two integer parameters defining the gradient and end point of the given line The analysis suggests a simple extension of Bresenham’s algorithm which provides an automatic shortcut (Computer Journal 25, 114)