摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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 sub-components to a predetermined level of decomposition.
摘要:
A method of producing a transform decomposition of data having an odd length the method comprising the steps of dividing the data into a portion having an even length of one element; performing a discrete wavelet transform on the even length data to produce low frequency subband data and high frequency subband data; adding the difference of the one element and an adjacent element to high frequency subband data. Preferably the transform is a Discrete Wavelet Transform utilised in the compression of image data.
摘要:
Methods, apparatus and computer program products for encoding and decoding transform coefficients are disclosed. A digital image (102) is input to a transform block (110), which preferably employs a discrete wavelet transform. A bit rearrangement block (120) codes bit sequences representing resulting transform coefficients (112) in an efficient fashion. The bit arrangement block (120) selects a portion of the coefficients as a region (200). The significance of each bitplane of the region (200) is scanned from most towards least significant bitplanes, and first and second tokens are provided for each insignificant and significant bitplanes until determining a significant bitplane. This region is then partitioned into subregions (210-216), which are each set as the selected region. This processing is repeated until a minimum bit level is reached, or the selected region has a specified size. The coefficients of specified-size regions (200-216) are coded and provided in a coded representation (122).
摘要:
A method of compressing a current image of a sequence of images. The current image is transformed with a predetermined transform to provide a set of transform coefficients, which are divided into blocks. An encoding termination condition is determined for at least one block, and the block is encoded in a series of coding passes. In a current coding pass, a performance measure is predicted, and encoding is terminated if the performance measure satisfies the encoding termination condition. Different color components may be given different weightings.
摘要:
Methods, computer program products and apparatuses are disclosed for processing images to detect and/or remove halftone. In one aspect, a portion of an image comprising a plurality of color channels is selected for processing (210), a frequency domain representation of the selected portion is generated for each color channel (220), data relating to predetermined regions in the frequency domain representations is processed (230), and halftone present in the selected portion is detected based on a result of the processing the data (240). In another aspect, an image is arranged into a plurality of bands each comprising a predetermined number of consecutive lines of pixels, each of the plurality of bands is arranged into a plurality of tiles of pixels, one of the plurality of tiles is selected as a selected portion, data relating to the selected portion is processed and halftone present in the selected portion is detected based on a result of the processing and on a result of processing at least one other portion of the image. Halftone may be detected based on spatial characteristics or frequency characteristics within the selected portion and detected halftone may be removed from spatial domain data or frequency domain data relating to the selected portion.
摘要:
The method performs a two-dimensional discrete wavelet transform on an image. The image comprises a plurality of blocks of pixels. The method generates (340) a current output block of subband data corresponding to a current block. The current output block is generated before either a one-dimensional discrete wavelet row or column transformation of a next block of pixels is completed, using intermediate lifting values stored (310, 350) during the generation of a plurality of previous blocks of subband data.
摘要:
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.