Showing papers on "Run-length encoding published in 1990"

A document skew detection method using run-length encoding and the Hough transform

Abstract: As part of the development of a document image analysis system, a method, based on the Hough transform, was devised for the detection of document skew and interline spacing-necessary parameters for the automatic segmentation of text from graphics. Because the Hough transform is computationally expensive, the amount of data within a document image is reduced through the computation of its horizontal and vertical black runlengths. Histograms of these runlengths are used to determine whether the document is in portrait or landscape orientation. A gray scale burst image is created from the black runlengths that are perpendicular to the text lines by placing the length of the run in the run's bottom-most pixel. By creating a burst image from the original document image, the processing time of the Hough transform can be reduced by a factor of as much as 7.4 for documents with gray-scale images. Because only small runlengths are input to the Hough transform and because the accumulator array is incremented by the runlength associated with a pixel rather than by a factor of 1, the negative effects of noise, black margins, and figures are avoided. Consequently, interline spacing can be determined more accurately. >

Bit-wise run-length encoding for data compression

Abstract: A method of compressing a digitized waveform into a sequence of N-bit words includes selecting corresponding bit values from N data words and generating a value based thereon. A next N input words are selected and the corresponding bits are used to generate a next value. The process is continued for each significant bit of the input sequence and the generated value stream is run-length encoded to produce a compressed data output stream.

Run length encoding method and system

Abstract: A run length encoder for converting bi-level video image data made up of white and black representative pixel values to a run length code to be used by a vector processor including a transition detector for detecting the transition of inputted image data values from either white to black or black to white. The inputted image data are addressed along each scanned line. At every white to black transition, the pixel address is stored in memory. The number of continuous black pixels following this first transition is counted until a black to white transition is detected. The resulting count value corresponding to each stored address value for each black "run" is also stored in memory, wherein these stored values represent the run length code of the video image data for use with the vector processor.

Picture data compression method

Abstract: PURPOSE:To prevent local deterioration in the quality of a reproduced picture by obtaining an AC component coefficient through the application of 2-dimension orthogonal conversion such a discrete cosine conversion DCT to a picture data, applying quantization, splitting the result into a bit plane and applying run length encoding compression while placing priority to the coefficient with larger absolute valve. CONSTITUTION:An orthogonal conversion section 1 splits a multi-gradation picture data into a block of M picture element X M picture element and used a DCT to apply NXN 2-dimension orthogonal conversion. The AC component from the orthogonal conversion section 1 is given to a compression section 2 to convert the AC component into a variable length code and to execute the run length encoding compression. The data compressed by run length encoding is given to an expansion section 3, the compression data is decoded to generate the original AC component. Then the decoded AC component is given to the orthogonal conversion section 4 together with the DC component from the said orthogonal conversion section 1 to apply inverse conversion to the DC and AC components to reproduce the original multi-gradation picture data.

Improved data compression apparatus

Abstract: The improved data compression system (100) concurrently processes both strings of repeated characters and textual substitution of input character strings. In this system (100), the performance of data compression techniques based on textual substitution are improved by the use of a compact representation for identifying instances in which a character in the input data stream is repeated. This is accomplished by nesting a run length encoding system (110) in the textual substitution system (111, 112, 120). This structure adds the recognition of runs of a repeated character before the processor performs the textual substitution data compression operation. A further performance improvement is obtained by expanding the alphabet of symbols stored in the compressor's dictionary (120) to include both the characters of the input data stream and repeat counts which indicate the repetion of a character. The handling of these repeat counts by the textual substitution based compression technique is no different than the handling of characters, or certain modifications are made in the handling of repeat counts.