Abstract: A method for converting an image from a bit map to a run end or run length representation includes the steps of: storing the image as a bit map representation; accessing for each byte in an image by a look-up table a selected routine, corresponding to such byte, from a number of routines for converting bit strings to run representations, wherein the look-up table accessed is selected in accordance with a color value of a preceding pixel binary bit; and executing the selected routine on the current byte to convert the bit string to a run representation; storing in a run representation buffer, as a count value, each run representation; repeating the above steps of accessing and executing for each byte and storing for each run of continuous color to the end of the image.

Abstract: Data compression for transfer (storage or communication) by a continuously adaptive probability decision model, closely approaches the compression entropy limit. Sender and receiver perform symmetrical compression/decompression of binary decision n according to probabilities calculated independently from the transfer sequence of 1 . . . n-1 binary decisions. Sender and receiver dynamically adapt the model probabilities, as a cumulative function of previously presented decisions, for optimal compression/decompression. Adaptive models for sender and receiver are symmetrical, to preserve data identity; transfer optimization is the intent. The source model includes a state generator and an adaptive probability generator, which dynamically modify the coding of decisions according to state, probability and bit signals, and adapt for the next decision.

Abstract: A method for rotating an image by 90 degrees includes the steps of: storing the image in a raster format arranged in r rows by c columns, image information in each row being stored in a number of bytes, each byte having b bits, there being c/b bytes in each row of the raster format; moving a block of the image into a temporary storage, there being r rows by v columns in the block; separating each image block into groups of bytes of rotatable size; determining for each group if all bits are the same value; rotating each group that does not have all bits the same value; storing each rotated group in an output area of the raster storage; repeating the above steps for all remaining blocks of the image.

Abstract: A method for converting an image from a bit map to a run end or run length representation includes the steps of: storing said image as a bit map representation; initializing all variables to be used in the conversion process; converting by table lookup, each run of continuous color to a run representation, storing, in a run representation buffer, as a count value, each run representation; repeating the steps of converting and storing for each run of continuous color to the end of the image.

Abstract: A method for converting an image from a run representation to a bit map, includes the steps of: storing a plurality of run representations of an image in a buffer; initializing a line of data; converting, by table lookup, each run representation, in said line, to a picture element representation, storing said picture element representation of said line; repeating the steps of initializing, converting and storing for remaining run representations until said image has been converted to a bit map representation.

Abstract: A method for expanding a binary image includes the steps of: storing the image in bit sequence; inserting for each string of 5 bits along a first axis one or more expansion bits, to convert each said string of 5 bits to a string of 6 bits; assigning a value to each expansion bit generated by the above step; inserting one or more rows of expansion bits for each 5 rows of bits along a second axis of the image to convert each 5 rows of bits to 6 rows of bits along the second axis of the image; assigning a value to each expansion bit generated by the above steps; storing the enlarged image generated by the above steps.

Abstract: Graphics images are generally considered to be those images comprised of text and/or line drawings. Data compression of graphics images is desired whenever a fast image transmission speed is desired in a limited band width channel. It is also used for storage of a large number of images in a limited capacity storage system. The method and apparatus described herein improves data compression, resolution and coding efficiency by eliminating transitions between gray levels at edges in an image, converting all gray levels to a common value to achieve a 3 level representation of a graphics image, and reversibly converting the 3 level representation to a bilevel double resolution representation by increasing the data sampling rate and therefore allowing the use of two level data compression techniques. A high resolution display or printed output may be obtained from the bilevel multiresolution representation.

Abstract: In an image processing system, a method is shown for efficiently transmitting data representing picture information in fields subsequent to a first field and for suppressing motion induced flicker in the processed image. Using previously processed first field data which is used to predict values for picture elements in subsequent fields, a gradient value is calculated which indicates relative picture activity. A difference value for the picture elements in the subsequent fields is calculated and is limited in magnitude by the gradient value for each picture element. The limited difference value is encoded as a function of previous difference value and transmitted to a remote location for decoding and picture reconstruction and display.

Abstract: 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.

Abstract: 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.

Abstract: A system for encoding images by assigning variable-length code words to fixed positions in a dynamic stack. Each position in the dynamic stack is occupied by a representation of an encodable image feature, such as a run-length or a vertical correlation. These codes are arranged in order of their respective frequencies of occurrence. The order in which these features are stacked is varied dynamically by the system, in accordance with their respective frequencies of occurrence and a predetermined scheme. Thus, the system can adapt to different types of documents being scanned, or to changes of scanning resolution. A relationship exists between the code words and the stack positions, which are not permanently assigned to specific image features. This arrangement ensures that the lengths of code words will be inversely related to their frequencies of occurrence under all conditions.

Abstract: 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.