Showing papers on "Run-length encoding published in 1995"

Run-length encoding/decoding video signals using scan patterns explicitly encoded into bitstreams

Abstract: Video signals are run-length encoded using a scan pattern and encoded video signals are run-length decoded using the scan pattern, where the scan pattern is explicitly encoded into the encoded bitstream. In a preferred embodiment, the scan pattern is generated by applying a constrained sorting rule to energy measures corresponding to the video signals to be encoded. The scan pattern used for encoding can be changed as often as needed where each new scan pattern is explicitly encoded into the bitstream for use in decoding.

Order preserving run length encoding with compression codeword extraction for comparisons

Abstract: The present invention provides a system and method for the dictionary ordering of keys after expansion, compression and concatenation of their key parts. After each key part has been expanded through padding, each substring of identical characters of length greater than or equal to three is compressed through run-length encoding algorithm. The substring is replaced by the sequence character, a compression identifying character and a number identifying the number of characters being replaced. After compression and the subsequent concatenation, the keys are compared character by character. At the first instance of a miscomparison, the comparison scheme performs a normal dictionary ordering if neither of the characters are part of a compression sequence. If a character at the point of miscomparison is part of a compression sequence then an ordering decision is made based on the compression character, the length of the compressed substring and the character following the compressed substring.

Encode and decode systems for image information

Abstract: (57) Abstract: A system for effectively performing run-length compression of multicolor image data is provided. In a method for compressing a bit string of a plurality of consecutive pixels (for example, CU02) based on a run length encoding method, run information for one compression unit (for example, CU02 *). Is the run length information indicating the number of consecutive identical pixel data blocks or the number of consecutive pixels (01 of the 3rd to 6th bits of CU02 *). 01) and; pixel data of 2-bit configuration showing the above-mentioned pixels by distinguishing three or more colors (01 of 7th to 8th bits of CU02 *) And

Method and apparatus for encoding and decoding digital image data

Abstract: An encoding method for digital image data comprising consecutive blocks of data groups having as content binary values always of an equal number of pixels of an image, utilizing a code which indicates that the encoded block is partly equal to the corresponding part of a reference block, the reference block preferably being the preceding block, and identifies the end point of that part of the reference block by reference to transitions in pixel value in the reference block. On decoding, that part of the reference block is taken over in the decoded block. This encoding method is, in practice, combined with run length encoding and encoding by copying an entire data group in the code.

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. >

Adaptive limitation of the dictionary size in LZW data compression

Abstract: Two modifications of the Lempel-Ziv-Welch (LZW) algorithm are presented to limit the dictionary size. First, a run-length encoding (RLE) is combined with the LZW algorithm, in order to preselect the input data. Then, a dynamic update of the dictionary is performed by eliminating the free branches in the tree representing the dictionary.

New block coding method for bilevel images

Abstract: A new block coding technique for the compression of bilevel text images is presented. The technique usesa combination of pre-processing the image to extract the edge information and block coding to compress thedata. The key feature of the technique is simplicity in implementation. The pre-processing consists of an imagedifferencing operation to decorrelate the strings of black pixels. The decorrelation is followed by the losslesscoding of each block of the image. The performance of the new image differencing (ID) method is examinedbased on both theoretical and experimental code length data. Both theoretical and simulation results show thatby pre-processing the image, the number of nonzero pixels can be significantly reduced and a more efficient blockcode is realized.Keywords: block coding, lossless compression, image differencing, run length encoding, fax coding, bilevelimage coding. 1 INTRODUCTION Zeng and Ahmed' and Kavalerchik2 have shown that sparse binary patterns (bilevel images) can be efficientlycoded using a technique known as block coding. Block coding takes advantage of the small number of blackpixels relative to the number of white pixels by breaking the image into blocks and only coding the blocks thatcontain black pixels. Zeng and Ahmed's (ZA) block coding scheme assumes random binary patterns and achievescompression if the density of black pixels is less than 19%. Most text documents are not well modeled as randombinary patterns. In fact, text documents typically contain strings of both black and white pixels in each row ofthe image. Therefore, if these strings are incorporated into the model, an alternative compression scheme maybe used. A two-step method is presented here and will be referred to as the image differencing (ID) block codingmethod. The ID method uses a differencing operation to decorrelate the pixels in a text image and produce datathat is well approximated to a random binary image. After the decorrelation step, a modification of the ZA block

Device and method for character font compression

Abstract: PURPOSE:To compress a character font which is plainly compressed and reducible in data volume. CONSTITUTION:This device is equipped with an M dividing means 4 which divides character font data into four, an encoding means 5 which judges whether or not there is black (1) in the divided data and encodes the data into 4-bit data, a judging means 6 which judges whether or not the data need to further be divided, a compressing means 7 which adds compression and restoration information, a run length table 8 where codes of short code lengths are assigned to 2X2-dot data (run length) that are high in occurrence frequency, and a run length encoding means 9 which encodes the run length according to the run length table 8.

Variable length coding method to be used in digitized video coding system

Abstract: PURPOSE: To encode a run length with a less number of bits by utilizing the relation between location of encoded data and a possible run length value. CONSTITUTION: Input data are supplied to a run length encoding block 10 and converted into a combined block containing one run length and its corresponding level. The combined block is inputted to a variable length encoding block 20 and it is checked whether or not the block is such a combination that in encoded by utilizing a prescribed variable length coding(VLC) table and occurs frequently. When the checked result is positive, encoding data are specified by utilizing the VLC table, and when the result is negative, the run length is transmitted to a receiver by encoding the run length by determining the number of the run length bits from the bit number table corresponding to the location of the run length and also the level being encoded to 6- or 12-bits depending upon the magnitude of the level. Thus, the run length can be encoded with a less number of bits.

Display system with data compression

Abstract: A display system for a portable computer having a liquid crystal display in which visual information is stored in a frame buffer 24, compressed and stored in its compressed form in a compressed data buffer 52 and then directed to the display. The system also includes and a data decompressor 30. Data is compressed by a microprocessor during idle times and decompressed on the fly. Such a system reduces power consumption. Data compression is achieved by run length encoding where a repeating character sequence is reduced to a single character plus an associated count of the number of times a character is repeated. Data is selected for compression on the basis of that count.

Encoding and decoding method and its device

Abstract: PURPOSE:To effciently execute entropy encoding and to improve the encoding compression rate of natural picture data by executing exclusive OR processing between a noticed picture element and its adjacent picture element on the prestage of entropy encoding. CONSTITUTION:Picture data PA from a picture input part 1 are applied to a bit plane developing part 2 and decomposed to a bit plane, which is stored in a picture memory 3. An exclusive OR operation part 4 forms exclusive OR between the picture data of each picture element position in the picture data of each bit plane stored in the memory 3 and that of an adjacent picture element adjacent to the preceding position of the picture element position concerned in a main scanning direction while using the contents of a work memory 5. The processed result is applied to a run length encoding processing part 6 as picture data PB. The processing part 6 applies prescribed run length encoding processing to the data PB to execute compression encoding and outputs encoded data CDa. Since entropy is reduced prior to encoding, the efficiency of encoding can be improved.

A Study on Compression and Decompression of Bit Map Data by NibbleRLE Code

Abstract: In this paper, a nibble RLE(Run Length Encoding) code for real time compression and decompression of Hanguel bit map font and printer data is proposed. The nibble RLE code shows good compression ratio in complete form Hangeul Myoungjo and Godik style bit map font and printer output bit map data. And two ASICs seperating compression and decompression are designed and simulated on CAD to verify the proposed code. The 0.8 micron CMOS Sea of Gate is used to implement the ASICs in amount of 2, 400 gates, and these are running at 25MHz. Therefore, the proposed code could be implemented with simple hardware and performs 100M bit/sec compression and decomression at maximum, it is good for real time applications.

Progressive Windowed JPEG Coder for Efficient Image Transmission

Abstract: Applications involving transmission of color images through low bandwidth telecommunication media involve a trade-off between image quality and decoding complexity. In this paper we investigate techniques that locally optimize the output quality of foreground objects in the decoded image, while obtaining significant gain by coarser coding of information of low interest areas of the image. High compression/quality ratios are achieved by introducing high-quality windows, as well as by using progressive coding principles in image filtering, and enhanced run length encoding techniques. The system described is currently fully operational and serving telemedicine image communication applications for remote diagnosis.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.