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    • 71. 发明授权
    • Adaptive graylevel image compression system
    • 自适应灰度图像压缩系统
    • US4725885A
    • 1988-02-16
    • US946542
    • 1986-12-22
    • Cesar A. GonzalesJoan L. MitchellWilliam B. Pennebaker
    • Cesar A. GonzalesJoan L. MitchellWilliam B. Pennebaker
    • H03M7/38G06T9/00H04N7/32H04N7/34H04N7/137
    • H04N19/124H04N19/50H04N19/593
    • Apparatus and method for modelling differential pulse code modulation (DPCM) input data for entropy coding. In particular, the sign and magnitude of one piece of DPCM data after another are modelled to provide a magnitude state input and a sign state input to provide context for DPCM magnitude input and DPCM sign input, respectively, to an entropy encoder or decoder. That is, the DPCM magnitudes of earlier pieces of (context) DPCM magnitude data are re-mapped for each such earlier piece of data, the re-mapped data being aggregated to form a combined value indicative of the magnitude state input. Similarly, the DPCM signs of earlier pieces of (context) DPCM sign data are re-mapped for each such earlier piece of data, the re-mapped data being aggregated to form a combined value indicative of the sign state input. In an image data compression system, the magnitude state input serves as an activity indicator for picture elements (pixels) neighboring a "subject" pixel. According to the invention, the DPCM signal is derived from a difference value calculated by subtracting one of a plurality of predictor values from the graylevel value X of the subject pixel. The selection of predictor value P is based on the value of the magnitude state (activity indicator). In addition, the difference value is subject to adaptive quantization in which one of a plurality of quantizers is employed in assigning the (X-P) difference value to a quantization level. The selection of quantizers is also based on the value of the magnitude state (activity indicator).
    • 73. 发明授权
    • Method and apparatus for compressing and decompressing strings of
electrical digital data bits
    • 用于压缩和解压缩电子数字数据位串的方法和装置
    • US4382286A
    • 1983-05-03
    • US164120
    • 1980-06-30
    • Joan L. MitchellPeter Quarendon
    • Joan L. MitchellPeter Quarendon
    • G06F5/00G06T9/00H03M7/30H04N1/415H04N7/12
    • H03M7/30
    • A compression technique for a character graphics system in which character cell definition bit strings are transmitted from a central processing unit to a display unit. Each cell is divided into a number of slices and each slice into digits. A test is made on whether to compress on a comparison with an all zero slice, the previous slice or the previous slice but one, depending upon the number of digit mismatches that occur when the comparison occurs. Slices are then compressed by comparing each digit with the corresponding digit in the comparison slice and generating a single 0 bit if the digit matches and including a 1 bit and the whole digit if a mismatch occurs. The compression in the central processing unit and the decompression in the display unit is implemented in microcoded routines.
    • 字符图形系统的压缩技术,其中字符单元定义位串从中央处理单元发送到显示单元。 每个单元被分成多个切片,每个切片分成数位。 测试是否根据比较发生时发生的数字不匹配的数量,与全零切片,先前切片或先前切片进行比较进行压缩。 然后通过将每个数字与比较片中的相应数字进行比较来压缩切片,并且如果数字匹配并且如果匹配发生则产生单个0比特,并且包括1比特和整数。 中央处理单元中的压缩和显示单元中的解压缩在微编码例程中实现。
    • 74. 发明授权
    • Gray scale image data compression with code words a function of image
history
    • 灰度图像数据压缩与码字是图像历史的功能
    • US4369463A
    • 1983-01-18
    • US270662
    • 1981-06-04
    • Dimitris AnastassiouJoan L. Mitchell
    • Dimitris AnastassiouJoan L. Mitchell
    • H04N1/411G06T9/00H03M7/40H04N1/41H04N7/26H04N7/30H04N7/32H04N7/12H03K13/22
    • H03M7/4006H04N19/124H04N19/50H04N19/13H04N19/60H04N19/91
    • The present invention relates to a method and apparatus for compacting gray-scale image data which maintains extremely good picture quality and can result in typical images in a compression ratio of 5 to 1 and even better if a final step of arithmetic coding is used. The method is a special application of adaptive differential pulse code modulation (DPCM) which utilizes a prediction of smoothness surrounding a current pel to determine variable length codes to convey the quantized error. Thus, a continuously adaptive variable length code is produced which may be accurately decoded without using any further marker (code indicator) bits. For each pel and "error bit" is generated to indicate to the decoder if the predicted quantization range is adequate. These eroror bits can be further significantly compressed.This method permits the use of a "zero bit" per pel mode for the data transmission (1 "error bit" per pel actually transmitted) and provides for the automatic detection of the particular variable length compression code utilized for transmitting the quantized error (E.sub.Y) for a particular pel. Utilizing the concepts of the present invention the inventors have obtained compression rates of approximately 1.5 bits per pel that produce a gray scale image at the decoding end of such a data transmission or storage system which has excellent quality (equal to 5 bit DPCM).By adding the concept of arithmetic coding to the previously set forth method, due to the nature of the statistical distribution of said special purpose error bit patterns, a compressed data set of less than 1 bit per pel has been achieved. This was produced from an original 8 bit per pel gray scale image.
    • 本发明涉及一种用于压缩灰度图像数据的方法和装置,其保持非常好的图像质量,并且如果使用算术编码的最后步骤,则可以以5比1的压缩比导致典型图像,甚至更好。 该方法是自适应差分脉冲编码调制(DPCM)的特殊应用,其利用对当前像素周围的平滑度的预测来确定可变长度码来传达量化误差。 因此,产生连续自适应可变长度码,其可以被准确地解码,而不使用任何进一步的标记(码指示符)比特。 对于每个像素,并且生成“错误位”以向解码器指示预测量化范围是否足够。 这些错误位可以被进一步显着压缩。 该方法允许使用每像素“零比特”进行数据传输(实际发送每像素1个“误差比特”),并且提供用于发送量化误差的特定可变长度压缩码的自动检测(EY )为特定的像素。 利用本发明的概念,本发明人获得了在具有优良质量(等于5位DPCM)的这种数据传输或存储系统的解码端产生灰度图像的大约每像素大约1.5位的压缩率。 通过将算术编码的概念添加到先前提出的方法中,由于所述专用误差位模式的统计分布的性质,已经实现了每像素小于1位的压缩数据集。 这是从原始的8位每像素灰度图像生成的。
    • 75. 发明授权
    • Two-dimensional image data compression and decompression system
    • 二维图像数据压缩和解压缩系统
    • UST985005I4
    • 1979-08-07
    • US951532
    • 1978-10-16
    • Gerald GoertzelJoan L. Mitchell
    • Gerald GoertzelJoan L. Mitchell
    • G06T9/00H04N1/417H04N7/32H04N11/04
    • H04N11/042H04N1/4175H04N19/93
    • a dual-mode encoding and decoding procedure enables image data to be compressed optionally in one-dimensional (1D) mode or two-dimensional (2D) mode. In 1D mode, color transitions in the image are encoded as run length features only. In 2D mode, the transitions are encoded as vertical correlation features wherever possible, and where this is not possible, the transitions are encoded as run length features. The compression achieved by run length encoding in 2D mode may be enhanced in those instances where the "history line" which precedes the current scan line contains a transition located between points that are vertically aligned with the beginning and end points of the run currently being encoded. Run length counting is suspended for those pels in the current run that could have been referenced to the history transition if the run had ended with any of these pels, thereby enabling the run to be encoded as though it contained fewer pels than its actual length. Compression may be enhanced still further by dynamically interchanging the variable-length bit patterns respectively representing certain vertical correlation and run length prefix codes depending upon whether the preceding transition was encoded as a vertical correlation feature or a run length feature.