Abstract: The method generates a compressed digital image from a original image. The compressed digital image allows random access to portions of the compressed image at a number of resolutions. The original image is first transformed (103) by a multi-level DWT to form a non redundant multiple resolution frequency domain representation of the image. The representation comprises a DC subband and a plurality of high frequency subbands arranged as levels, where each level represents a frequency contribution between adjacent resolutions and where each subband comprises a plurality of tiles. The DC subband is then entropy encoded (104) into the bitstream. The high frequency subbands are next entropy encoded (108,109, and 110) into the bitstream in level order (105,113,114) and tile order (107,111).

Abstract: A method of compressing a current image of a sequence of images is disclosed. Firstly, the current image is transformed with a predetermined transform such as the DWT to provide a set of transform coefficients (step 2202). The method then retrieves (step 2303), for at least one transform coefficient of a current image, a predetermined number of bits, preferably two, of a corresponding transform coefficient of a previously compressed image of the sequence. The corresponding transform coefficient is truncated at a truncation bitplane and the retrieved bits are the least significant bits of the truncated corresponding transform coefficient. The transform coefficient of the current image is set to a new value that is a function of the retrieved bits (step 2306) and bits of the transform coefficients of the current image are stored for use in compressing one or more subsequent images of the sequence (step 2208).

Abstract: The method generates a compressed digital image from a original image. The compressed digital image allows random access to portions of the compressed image at a number of resolutions. The original image is first transformed (103) by a multi-level DWT to form a non redundant multiple resolution frequency domain representation of the image. The representation comprises a DC subband and a plurality of high frequency subbands arranged as levels, where each level represents a frequency contribution between adjacent resolutions and where each subband comprises a plurality of tiles. The DC subband is then entropy encoded (104) into the bitstream. The high frequency subbands are next entropy encoded (108,109, and 110) into the bitstream in level order (105,113,114) and tile order (107,111).

Abstract: A method (300) of encoding an image into an image code-stream. The method (300) generates a reduced resolution representation of the image and encodes the reduced resolution representation in accordance with a multi-resolution format to form an encoded reduced resolution representation of the image. The encoded reduced resolution representation is embedded into a first portion of the image code-stream and a compressed representation of the image is encoded into a further portion of the image code-stream.

Abstract: The method encodes a digital image to provide a compressed coded representation of the image. The method firstly performs a multi-level 2-D DWT transform (410) on the entire image, which is arranged in a hierarchical order (420). The sub-bands of the transform are then tiled (430) into a number of blocks. The method then embed-bitplane encodes (440) each block to visually lossless point. Afterwards, each encoded block is terminated (450) at a bitplane that minimizes image distortion based on determined distortion measures and a desired total of determined block rates. Finally, the method concatenates (460) the said terminated encoded blocks to form the coded representation.

Abstract: An apparatus includes a DCT unit for transforming blocks of pixels into respective blocks of transform coefficients, entropy encoders for encoding respective partitions of the DCT blocks where at least one partition comprises bit-plane data from each block of transform coefficients, and a scan output manager for storing the entropy encoded partitions in a buffer of fixed memory size. The manager manages the storing of the coded partitions in the buffer whereby during the storing of the coded partitions if it is determined the buffer is full, a coded least perceptually significant partition currently stored in the buffer is overwritten by data from a coded more perceptually significant partition.

Abstract: The method encodes a digital image to provide a compressed representation of the image. The method initially performs a multi-level 2-D Discrete Wavelet Transform on the digital image, which is arranged in a hierarchical order of sub-bands. The method then tiles each sub-band to form a number of blocks of transform coefficients. The method then encodes each bitplane of each block from a maximum bitplane to a minimum bitplane in the following manner. The method divides a current bitplane into a number of first areas and/or a number of second areas, wherein each first area comprises a number of coefficients having corresponding most significant bits in the current bitplane or less and each second area comprises a number of coefficients having corresponding most significant bits in a bitplane greater than the current bitplane. The method then codes the significance of each first area in the current bitplane; and codes a corresponding bit of each coefficient in each second area of the current bitplane.

Abstract: A method of reconstructing an image, where the input image data is preferably part I or part II compliant JPEG2000 coded data, or pixel data of the original image. The method selects (810) an output resolution R, and then determines a number of sub-passes to extract from each block code based on the selected resolution. The method then extracts (830) the determined sub-passes and the remaining sub-passes are discarded. The method then reconstructs 840 the image from the extracted sub-passes. The reconstructed image can be in the form of the selected resolution of the original image, or it can be in the form of compressed image data of the selected resolution of the original image.

Abstract: The apparatus comprises a discrete wavelet transform (DWT) engine, a code block manager, and an entropy encoder. The code block manager comprises at least one controller, which losslessly compresses the transform coefficients and stores them in a code block storage for buffering. The entropy coder comprises at least one entropy encoder, each comprising a decoder for decoding the losslessly compressed transformed coefficients prior to entropy encoding.

Abstract: The method decompresses blocks of a compressed image (202,204,206,208) and boundary filters the blocks (210). The method one-dimensionally filters across those boundary regions having a common boundary in accordance with a predetermined formulae, wherein the one-dimensional filtering is applied perpendicular to the common boundary.

Abstract: The method of encoding divides the image into a number of blocks, which are then transformed (200), in accordance with a linear transform, into blocks of transform coefficients. The transform coefficients are rearranged (202) into a set of groups, wherein subsets of the groups of coefficients are capable of being inversed transformed to reproduce the image or a resolution thereof. The groups (203) are then encoded in turn. In the method of decoding, a user first selects a resolution mode and the method decodes (300) a predetermined number of groups in response to said resolution mode. The method then rearranges (301) the decoded groups to form blocks of transform coefficients, wherein the arrangement is determined in response to the resolution mode. The method then inverse transforms said rearrangement (303), if necessary, wherein the inverse transform is dependent on the resolution mode and combines the blocks of pixels to reconstitute the image or a resolution thereof.

Abstract: The method decodes an compressed representation of a digital image. The compressed representation is in the form of a bitstream comprising in sequence encoded bitplanes each having first portions representative of the significances of first sub-regions in the current bitplane and second portions representative of respective bits of each coefficient in second sub-regions of the current bitplane. The method decodes each bitplane of a block of transform coefficients from a maximum bitplane to a minimum bitplane in the following manner. The method decodes the first portion as the respective significances of the first sub-regions in the current bitplane and decodes the second portion as the respective bits of each coefficient in the second sub-regions of said current bitplane.

Abstract: A method inverse discrete wavelet transforms subband data in segments and maintains a state between segments. The method selects (840, 850) one of a plurality of different computational procedures for performing the inverse DWT by testing the state and the subset of the current segment of subband data to determine if a current segment can be inverse transformed with a reduced computation procedure (860). If the test is positive the method performs the inverse DWT using said reduced computation procedure; otherwise the method performs the inverse DWT of the segment using another procedure (860).

Abstract: Apparatus 100 is disclosed that comprises a DCT unit 104 for transforming blocks of pixels into respective blocks of transform coefficients, entropy encoders 106(1), . . . 106(18) for encoding respective partitions of the DCT blocks where at least one partition comprises bit-plane data from each of the block of transform coefficients, a scan output manager 108 for storing the entropy encoded partitions in a buffer 110 of fixed memory size. The manager 108 manages the storing of the coded partitions in the buffer 110 whereby during the storing of the coded partitions if it is determined the buffer 110 is full, a coded least perceptually significant partition currently stored in the buffer 110 is overwritten by data from a coded more perceptually significant partition.

Abstract: The apparatus (300) comprises a DWT engine (308), a code block manager (310) and entropy encoder (314). The code block manager (310) comprises at least one controller (412, 414, and 416), which losslessly compress the transform coefficients and stores them in a code block store (418) for buffering. The entropy coder (314) comprises at least one entropy encoder (422, 424, 426), each comprising a decoder (1206, 1204,) for decoding the losslessly compressed transformed coefficients prior to entropy encoding (1202).

Abstract: A method of compressing digital data is disclosed including the steps of transforming the data utilizing a discrete wavelet transform to produce corresponding transformed data; quantizing the transformed data utilizing a variable quantization determined by a corresponding quadtree structure wherein each of the quadtree leaf nodes has an associated quantization factor utilized in the quantizing of the transformed data. Preferably, the quadtree is determined to be an optimum in a rate distortion sense and encoded utilizing a binary prefix notation followed by a list of quantization factors. The method of Lagrange multipliers can be utilized to determine the optimum to a predetermined number of bits per data item. The present invention has particular application to image data or to video data and in particular frame difference data.

Abstract: A method of retrieving an image for display is disclosed. The image is stored in a compressed wavelet-based format having blocks encoded substantially independently. Initially, a representation (1300) of the image is provided at a first (low) resolution (1302). The user can then select a portion (1308) of the representation for reproduction at a predetermined, generally a second (higher), resolution. A first set of blocks is then identified (1322) corresponding to the selected portion(1310), which are then retrieved, decompressed and rendered to display. A second set of blocks (associated with the first set of blocks) is then identified (1326-1340), retrieved and decompressed. The rendered first set of blocks is then modified using the decompressed second set and displayed at the predetermined/second resolution.

Abstract: A method of representing a digital image to provide a coded representation is disclosed. The digital image is divided into a number of blocks of pixels and each block is transformed to derive a block of transform coefficients, each transform coefficient being represented by a predefined bit sequence. Each block of transform coefficients is selected in turn as a region and a predetermined maximum bit plane is set as the current bit plane. This is followed by scanning the significances of each bitplane of the selected region from the current bitplane towards a predetermined minimum bitplane, and providing a first token for each insignificant bitplane and a second token for a significant bitplane in the code representation until a significant bitplane is determined and the determined significant bitplane is set as the current bitplane. The selected region is partitioned into two or more subregions having a predetermined form, and setting each of the subregions as the selected region.

Abstract: A method is disclosed for recovering image memory capacity, in relation to an image which has been encoded using a linear transform according to a layer progressive mode into L layers, L being an integer value greater than unity, the L layers being stored in an image memory having a limited capacity. The method comprises defining a Quality Reduction Factor (700), being a positive integer value, identifying at least one of the L layers corresponding to the Quality Reduction Factor, and discarding (702) said at least one of the L layers in progressive order in accordance with the Quality Reduction Factor, thereby recovering said memory capacity.

Abstract: A method of creating a wavelet decomposition of a collection of data values is disclosed, the method including the steps of performing an initial decomposition of the data values into a series of components having low frequency components, high frequency components and components having a mixture of high and low frequencies; determining a first number of coefficients of each of the components having a magnitude exceeding a predetermined component threshold; creating a decomposition of each of the components into a series of sub components having low frequency sub-components, high frequency sub-components and sub-components having a mixture of high and low frequencies; determining a second number of coefficients of each of the sub-components having a magnitude exceeding a predetermined sub-component threshold; utilizing the first number and the second number to determine if the component should be decomposed into sub-components; and where the decomposition proceeds, applying the previous steps to each of the s