Abstract: Methods for reversible data hiding are disclosed herein. These methods may be applied to images for reversible image data hiding. In one embodiment, a method for reversible data hiding comprises identifying carrier data having a plurality of components and establishing prediction-errors for each of the components of the carrier data. A first threshold and a second threshold are established. The prediction-errors of the components are evaluated against the first threshold to identify components for possible hiding. The components identified for possible hiding are evaluated against the second threshold to identify components for hiding. To-be embedded data is embedded into the carrier data identified for hiding to create marked data. The marked data is evaluated for overflow or underflow. If overflow or underflow is detected, histogram modification is performed. Marked data is then established.

Abstract: A method for estimating quality of images compressed with a transformation based compression method. The estimation method uses estimated errors generated by quantization to obtain an image quality indicator and does not require use of a reference image. The estimation method includes calculating a probability of at least one specific quantized transformation coefficient value for at least all coefficients representing one identical two-dimensional frequency, and estimating identifying parameters of at least one probability density function of non-quantized coefficient values from the quantized coefficient value probabilities, with a type of probability density function being preset. The estimation method further includes calculating an image quality indicator from errors introduced by quantization, which are derived from probability density function parameters and quantization parameters.

Abstract: A system and method for updating a display unit remotely located from a computing system are described. The method includes copying display information from a video buffer of a computing device executing an application to generate a display update, calculating a size of the display update, and determining an amount of available bandwidth of a network connecting the computing device and the display unit. The method also includes calculating a time period required to communicate the display update from the computing device to the display unit, transmitting the display update to the display; and repeating the method after the time period has elapsed.

Abstract: A video encoding method and apparatus is shown wherein image information is represented as a plurality of pixels, the pixels are organized into blocks, pixels transposition is performed on image information at the boundaries of the blocks, the blocks are transform coded and quantized. Pixel transposition involves transposition of alternate pixels at the boundaries of blocks with pixels of neighboring blocks found in a pre-determined direction. The pre-determined direction may be fixed by a system or may be applied on an image by image basis. In the event that the pre-determined direction is not established by a system, a pixel transposition circuit includes a transposition keyword in the output bit stream which is used by a decoded to determine the direction of pixel transposition.

Abstract: An image compression apparatus performs quantization of DC component data, low-pass component data and high-pass component data which are generated by frequency conversion of still image data. An extracting part extracts additional data and coding object data which is to be entropy coded, from quantization data. An entropy coding part performs entropy coding of the coding object data stored in a coding object data memory. An additional data processing part generates a flex bit from the additional data. A pattern information generation part acquires the coding object data directly from the extracting part, to generate pattern information indicating whether the coding object data is zero or not. A bit stream generation part outputs the pattern information, the coding object data and the flex bit in a predetermined order, to output a bit stream.

Abstract: A method and system for coding mode selection using estimated coding costs. To provide high compression efficiency, for example, an encoding device may attempt to select a coding mode for coding blocks of pixels that codes the data of the blocks with high efficiency. To this end, the encoding device may perform coding mode selection based on estimates of coding cost for at least a portion of the possible modes. The encoding device may estimate the coding cost for the different modes without actually coding the blocks. In fact, in some aspects, the encoding module device may estimate the coding cost for the modes without quantizing the data of the block for each mode. In this manner, the coding cost estimation techniques may reduce the amount of computationally intensive calculations needed to perform effective mode selection.

Abstract: A method and apparatus compress projection data and store the compressed projection data in a rotatable part that is mounted for rotation within a stationary part. The data acquisition source, compressor and storage device are connected to the rotatable part. The compressor compresses projection data samples provided by the data acquisition source to form compressed packets. The compressed packets are stored in the storage device, for example one or more solid state drives mounted on the rotatable part. A data access array contains information related to the location of the stored compressed packets. Compressed packets are retrieved and transferred across the interface to the stationary part. A decompressor at the stationary part decompresses the received compressed packets to form decompressed samples of the corresponding projection data. This abstract does not limit the scope of the invention as described in the claims.

Abstract: An amount-of-compressed-data control method applicable to image data compression processing for compressing an amount of data is disclosed. The method includes the steps of: performing quantization by: dividing one digital image into multiple blocks each having n×n pixels; performing orthogonal transform on each block; and dividing n×n conversion coefficients resulting from the conversion by each threshold value of a quantization matrix including n×n threshold values each resulting from the multiplication of a predetermined coefficient S (where S is a positive real number); and variable-length encoding the quantized data.

Abstract: An image information decoding method for decoding compressed image information which has been coded via a process including dividing an input image signal into blocks, performing an orthogonal transform on the blocks on a block-by-block basis, and quantizing resultant orthogonal transform coefficients. The decoding process includes performing dequantization such that a quantization parameter is weighted by an addition operation, and the dequantization is performed on each chroma components of the quantized coefficients using said weighted quantization parameter, and performing an inverse orthogonal transform.

Abstract: An image information decoding method for decoding compressed image information in an image decoding apparatus, which has been coded via a process including dividing an input image signal into blocks, performing an orthogonal transform on the blocks on a block-by-block basis, and quantizing resultant orthogonal transform coefficients. The decoding process includes performing, in a dequantization unit in the image decoding apparatus, dequantization such that a quantization parameter is weighted by an addition operation that adds the weight by addition, and the dequantization is performed on each chroma and luma component of the quantized coefficients using quantization step sizes, said luma component being weighted by the quantization parameter; and performing, in a transform unit in the image decoding apparatus, an inverse orthogonal transform.

Abstract: A decoding apparatus (100) according to the present invention includes: a decoding unit (101) which decodes identification information identifying an orthogonal transform basis for inverse orthogonal transform; an orthogonal transform basis accumulation unit (110) accumulating orthogonal transform bases for inverse orthogonal transform; an orthogonal transform basis storage unit (103) storing an orthogonal transform basis for inverse transform, from among the stored orthogonal transform bases; an inverse orthogonal transform unit (112) which performs inverse orthogonal transform using the identified orthogonal transform basis; and an orthogonal transform basis transfer control unit (102) which transfers the identified orthogonal transfer basis from the orthogonal transform basis accumulation unit (110) to the orthogonal transfer basis storage unit (103) only when the identified orthogonal transform basis is not yet stored therein.

Abstract: Methods and devices for encoding and decoding data using adaptive transform domain filtering are described. The encoder determines a set of transform domain filter coefficients to be applied to a transform domain prediction. The filtering may, in some cases, also apply to quantized transform domain coefficients. Rate-distortion optimization may be used to determine the optimal filter coefficients on a frame-based, coding-unit-basis, or other basis.

Abstract: In an image encoder, a first quantization section which is selected when normal image quality is required performs quantization by dividing a wavelet transformation coefficient by a quantization step size and by thereafter rounding down a fraction thereof. On the other side, a second quantization section which is selected when high image quality is required performs quantization by dividing a wavelet transformation coefficient by a quantization step size, by adding 0.5 to the addition result, and by thereafter rounding down a fraction thereof. Therefore, the width of a dead zone where coefficients are quantized to a value of 0 is narrower than that in the first quantization section, and higher image quality is obtained accordingly.

Abstract: A motion image decoding apparatus for generating a prediction signal in blocks is provided with a low-resolution block decoder for generating a low-resolution block with a smaller number of pixels than that of a prediction block by decoding encoded data. The motion image decoding apparatus is further provided with an enhanced block generator for enhancing a low-resolution block generated by a decoded low-resolution block to a block with the same number of pixels as that of the prediction block using a decoded image. Furthermore, the motion image decoding apparatus is provided with a block divider for generating plural small blocks by dividing an enhanced block based on a predetermined division rule and a small block predictor for generating a predicted small block of a small block using a decoded image and the plural small blocks.

Abstract: A watermark information embedding apparatus generates a document image from electronic document data that has been input thereto, modifies the electronic document data based upon the document image and embeds information in the electronic document data. The apparatus includes a document image generator for generating a document image from the electronic document data; a document analyzer for detecting layout information of each constituent image in the generated document image; a normalization information calculation unit for calculating normalization information, which is for normalizing placement of each constituent image, based upon the detected layout information; a modification unit for modifying the electronic document data; and an embedding unit for embedding information in the modified electronic document data.

Abstract: Systems and methods are presented for accelerated image rendering. In one implementation, the systems and methods receive digital image data and derive intermediate data associated with the digital image data to accelerate image rendering.

Abstract: A method and an apparatus to encode a series of quantized coefficients of a transform of a block of image data. The transform is such that 0 is the most likely coefficient amplitude and 1 is the next most likely coefficient amplitude. The method includes forming symbols (called events) from the series of quantized transform coefficients. An event is a run of none or more zero-valued coefficients followed by a run of one of a predefined set of sequences, each sequence in the set being either a single coefficient of amplitude greater than one, or a sequence of 1's and 0's starting with a coefficient of amplitude 1. The method includes forming a codeword for each formed event. Relatively short codewords are formed to represent events that are relatively more likely to occur, and relatively long codewords are formed to represent events that are relatively less likely to occur.

Abstract: Apparatus, systems and techniques based on an integer transform for encoding and decoding video or image signals, including transform of encoding and decoding of image and video signals and generation of an order-2N transform W from an order-N transform T in the field of image and video coding. For example, a retrieving unit is configured to retrieve an order-N transform T, where N is an integer; a deriving unit is configured to derive an order-2N transform W from the retrieved order-N transform T, and a transforming unit configured to generate an order-2N data Z using the derived transform W.

Abstract: In an embodiment, a compression unit is provided which may perform compression of images with low latency and relatively little hardware. Similarly, a decompression unit may be provided which may decompress the images with low latency and hardware. In an embodiment, the transmission of compressed coefficients may be performed using less than two passes through the list of coefficients. During the first pass, the most significant coefficients may be transmitted and other significance groups may be identified as linked lists. The linked lists may then be traverse to send the other significance groups. In an embodiment, a color space conversion may be made to permit filtering of fewer color components than might be possible in the source color space.

Abstract: A method of and an apparatus for encoding and decoding using transformation bases of a yet higher efficiency. In a method for encoding an object signal in compliance with a transformation rule, a signal correlating to the object signal is obtained, and a transformation base that forms the transformation rule is derived based on a characteristic of the obtained reference signal. The object signal is transformed and encoded in compliance with the transformation rule based on the derived transformation base. Accordingly, the object signal is transformed in compliance with the transformation rule based on the transformation base derived from the characteristic of the reference signal. Since the reference signal is correlated to the object signal, the transformation base derived from the characteristic matches the feature of the object signal.

Abstract: A method and system generates and compares fingerprints for videos in a video library. The video fingerprints provide a compact representation of the spatial and sequential characteristics of the video that can be used to quickly and efficiently identify video content. Because the fingerprints are based on spatial and sequential characteristics rather than exact bit sequences, visual content of videos can be effectively compared even when there are small differences between the videos in compression factors, source resolutions, start and stop times, frame rates, and so on. Comparison of video fingerprints can be used, for example, to search for and remove copyright protected videos from a video library. Further, duplicate videos can be detected and discarded in order to preserve storage space.

Abstract: A data compressing method comprises first step in which a data is orthogonally transformed so that an orthogonal transform data is generated. A processing step executed subsequent to the first step is divided into a processing step for an alternate-current component of the orthogonal transform data and a processing step for a direct-current component of the orthogonal transform data. The processing step for the direct-current component includes a second step in which an inverse transform equivalent to a decoding process of the orthogonal transform data is executed on the orthogonal transform data.

Abstract: In a case where a padded orthogonally transformed block obtained by orthogonally transforming a padded image block of 8×8 pixels to which padding data has been added has been recorded as compressed image data, the padded orthogonally transformed block is subjected to an inverse orthogonal transformation to thereby restore the padded image block. Padding data contained in the restored padded image block is replaced with a portion obtained by copying a portion of the original image, thereby generating a modified image block. In a case where the true width of an edge pixel corresponding to an edge among the pixels forming the image block is less than 0.5, the pixel is obtained by adjusting the level of a pixel adjacent to the edge pixel in such a manner that it will have a level conforming to the width and level of the edge pixel.

Abstract: Described herein are methods and devices for encoding and decoding data. An encoding device can be configured to encode video by performing intra-frame encoding using wavelet transformation. The encoding device can include a generation unit configured to generate a composite image for every n temporally consecutive frames, and an encoding unit configured to perform the encoding for the composite image. The decoding device can be configured to decode data encoded by such an encoding device.

Abstract: A method performs inverse tone mapping of an image in a decoder. For each block of each color channel of the image the following steps are performed. A scaling factor is determined for a current block of the image by adding a predicted scaling factor for the current block to a difference between the predicted scaling factor and the scaling factor of an adjacent block. An offset value for the current block is determined by adding a predicted offset for the current block to a difference between the predicted offset value and the offset value of the adjacent block. The scaling factor and the offset value are applied to pixel intensity values of the current block to produce a mapped block in which a bit-depth of the mapped block is greater than the bit-depth of the current block.

Abstract: Provided are a method and apparatus for transforming an image, in which an input image is transformed into a frequency domain by selectively using a plurality of frequency transform algorithms according to a frequency characteristic of the input image. The method includes: selecting a frequency transform algorithm to be used for a current block from a plurality of frequency transform algorithms according to a result obtained by transforming frequencies of peripheral blocks adjacent to the current block; and transforming the current block into a frequency domain by using the selected frequency transform algorithm.

Abstract: Processing of at least one digital image includes performing first and second separable block transforms in first and second directions; modifying results of the second block transforms; and performing first and second separable inverse block transforms in the first and second directions on the modified results. Transform coefficients are re-used while performing at least one the transforms. The processing can be performed on 2-D signals such as still images and 3-D signals such as video.

Abstract: The image processor 1 includes a frequency transform unit 12, an encoding unit 15, and a memory 4. The encoding unit 15 includes a DC processing unit 31 that generates a direct-current stream, an LP processing unit 32 that generates a low-frequency stream, an HP processing unit 33 that generates an upper high-frequency stream and a lower high-frequency stream, and an output unit 34 having output ports 41 to 44 to output the direct-current stream, the low-frequency stream, the upper high-frequency stream, and the lower high-frequency stream to the memory 4.

Abstract: Scanning image data and target image data are respectively stored in a first storage area and a second storage area. In one case, (J?M+1)×(K?N+1)×M×N pieces of pixel data are stored as comparison image data relating to all comparison areas, and M×N pieces of pixel data are stored as target image data. In contrast, the present invention requires the storage only of J×K pieces of pixel data as scanning image data, and M×N pieces of pixel data as target image data. This means the number of pieces of pixel data to be stored is reduced. In the case discussed above, one piece of target image data and (J?M+1)×(K?N+1) pieces of pixel data relating to all comparison areas and corresponding to this target image data are stored. As compared to this case, the number of times pixel data are retrieved is reduced to 1/(M×N), thereby shortening processing speed.

Abstract: A method of reducing computations utilizing a threshold to increase efficiency and speed of a video encoder is described. Computations of transform and scaling processes of a video encoder are able to be streamlined by utilizing one or more thresholds stored within one or more lookup tables. A selected threshold is compared with a value before scaling. If the value before scaling is less than the threshold, it is known that the coefficient will be zero and thus no further computations are required. Furthermore, the coefficient is set to zero. If the value before scaling is greater than the threshold, then further calculations are performed. The method is able to be extended to eliminate computations in forward transform as well. By skipping computations when the coefficient is zero, the method eliminates wasted computation power and time.

Abstract: Provided is an apparatus and method for transforming between a DCT coefficient and a DWT coefficient. The transforming apparatus includes a first fundamental matrix calculating unit, a second fundamental matrix calculating unit, and a DWT coefficient calculating unit. The first fundamental matrix calculating unit calculates a first fundamental matrix by multiplying an N×N forward DWT transform matrix and an N×N matrix that has diagonal components corresponding to a transpose matrix of an 8×8 DCT transform matrix and the remaining components corresponding to an 8×8 matrix with all elements being zero. The second fundamental matrix calculating unit calculates a second fundamental matrix by multiplying an M×M matrix, which has diagonal components corresponding to an 8×8 DCT transform matrix and the remaining components corresponding to an 8×8 matrix with all elements being zero, and a transpose matrix of an M×M forward DWT transform matrix.

Abstract: Video is encoded by applying a vertically and horizontally separable transform to provide a block of transform coefficients; and quantising the transform coefficients. Prior to quantisation, a filtering operation is performed on the block of transform coefficients, the filtering operation applying a rotation to pairs of coefficients in the block. Each pair of coefficients may be symmetrically positioned with respect to the leading diagonal of the block.

Abstract: Low complexity (16 bit arithmetic) video compression has 8×8 block with transforms using 8×8 integer matrices and quantization with look up table scalar plus constant right shift for all quantization steps. Inverse quantization also a look up table scalar plus right shift dependent upon the quantization step and inverse transform using the 8×8 integer matrices.

Abstract: The present invention relates to a method of converting the size of an image, i.e., resolution of an image, and more specifically, to a method of reducing or enlarging the size of an image using coefficients of integer discrete cosine transform (Integer DCT), which is a type of block transform. Since the method of reducing and enlarging the size of an image according to the present invention reduces or enlarges the size of an image through an integer operation, hardware can be implemented using shifts and additions, and therefore, complexity of the hardware may be lowered, and the method of the present invention provides images of a good quality that is almost the same as the quality of an image provided according to a conventional method of reducing and enlarging an image using real-number DCT coefficients. The method of reducing and enlarging the size of an image according to the present invention is compatible with a H.264/AVC codec.

Abstract: In response to a request from a client, a server for volume rendering loads a volume dataset from a storage archive, creates a low resolution sub-sampled copy of such volume dataset and transmits it to a client. In response to subsequent requests from the client, the server for volume rendering renders a high quality image of the full resolution volume dataset and renders a low quality image of the sub-sampled copy of the volume dataset, then generates a pixel mask or a hybrid pixel mask indicative of a difference between the high quality image and the low quality image and transmits such pixel mask to the client. The client receives from the server the pixel mask and computes a high quality image based at least in part on the pixel mask and on a selective rendering of its local low resolution sub-sampled copy of the volume dataset.

Abstract: A method and apparatus are disclosed herein for spatial sparsity induced temporal prediction. In one embodiment, the method comprises: performing motion compensation to generate a first motion compensated prediction using a first block from a previously coded frame; generating a second motion compensated prediction for a second block to be coded from the first motion compensated prediction using a plurality of predictions in the spatial domain, including generating each of the plurality of predictions by generating block transform coefficients for the first block using a transform, generating predicted transform coefficients of the second block to be coded using the block transform coefficients, and performing an inverse transform on the predicted transform coefficients to create the second motion compensated prediction in the pixel domain; subtracting the second motion compensated prediction from a block in a current frame to produce a residual frame; and coding the residual frame.

Abstract: Even in a case where there are a plurality of syntax elements, the invention reduces influence of the number of syntax elements and realizes high-speed encoding. An apparatus comprises N number of codes generation units arranged in parallel, which are configured to generate codes, including one or more codes, based on a transform coefficient; N number of first code concatenation units arranged in parallel, each of which is configured to concatenate the codes, respectively generated by the N number of codes generation units, for generating a code stream; N number of storage units arranged in parallel, each of which is configured to store the N number of code streams inputted from the N number of first code concatenation units; and a second code concatenation unit configured to read each of the code streams, which are stored in the N number of storage units, and concatenate the read code streams.

Abstract: In an image forming apparatus includes a quantization threshold value to convert input image data of an N value to output image data of an M value based on random dither processing. A flag to designate addition of a non-periodic component to a quantization threshold value can be set for each quantization threshold value and a threshold value that has a non-periodic component is added to the quantization threshold value based on a relation between a large and a small quantization threshold value in different threshold value levels with respect to any target pixel in the quantization threshold value.

Abstract: A coding method conversion apparatus converts the first coded data coded by the first coding method into the second coded data. The coding method conversion apparatus includes: an H.264 decoder which decodes the first coded data; a deblocking filter strength calculation unit which calculates a filter strength of deblocking filtering of a second coding method, using at least one piece of decoding information except a coding type of the first coded data, the decoding information being obtained by decoding the first coded data; and a deblocking filter which performs the deblocking filtering to reduce noise in a boundary of blocks according to the filter strength calculated by the deblocking filter strength calculation unit.

Abstract: An image capturing apparatus 100 first executes JPEG encoding on RAW data. On the basis of the compression ratio of JPEG image data obtained, the image capturing apparatus 100 selects a Huffman table to encode the RAW data. With the higher compression ratio of the JPEG data obtained, the image capturing apparatus 100 assumes that the RAW data is image data with a larger number of low frequency components. The image capturing apparatus 100 thus selects a Huffman table that assigns a particularly short code to a predictive differential value with a smaller absolute value. In contrast, with the lower compression ratio of the JPEG image data obtained, the image capturing apparatus 100 selects a Huffman table that assigns a code of a relatively equal length to the predictive differential value regardless of its absolute value.

Abstract: This invention decreases the count of access to a memory which stores image data regarding orthogonal transform, and quickly generates orthogonal transform coefficients. An apparatus includes a storage unit which stores image data, a memory controller which reads each block from the storage unit, a first transforming unit which receives and orthogonally transforms the input block, and calculates only one DC component, a selector which selects and outputs one of the block read out via the memory controller, and data of DC components from the first transforming unit that are equal in number to pixels included in the block, a second transforming unit which orthogonally transforms data that have been output from the selector and are equal in number to pixels included in the block, and outputs either one DC component or a plurality of AC components, and a controller which controls the memory controller, selector, and second transforming unit.

Abstract: Using scan conversion processing of changing the scan order for each block, parallel scan conversion processing is executed if possible. A scan status holding unit holds statistical information based on the appearance frequency values of coefficients in a block. A scan order holding unit holds coefficient position information in which the coefficient positions in a block are arranged based on the scan order. A significant data position information generation unit scans one block data in accordance with coefficient position information, and generates information representing nonzero/zero for each data position. Based on the statistical information and the information generated by the significant data position information generation unit, a parallel number determination unit determines whether to process two blocks in parallel or process one block. In accordance with the determination, a scan conversion unit scan-converts two input blocks in parallel or scan-converts only one of the blocks.

Abstract: An apparatus and method encodes into block units an image in which halftone images and character and/or line images are mixed, and makes a substitution value, substituting for pixels in which pixels of a character and/or line image exist, a value whereby the occurrence of quantization errors of direct current components after frequency conversion is substantially zero, thereby minimizing block distortion of images when decoding. Therefore, a blocking unit inputs images in 8×8 pixel blocks. An acquisition unit acquires pixel data of character and/or line images as acquisition color information and acquires identification information identifying character and/or line image pixel positions. A substitution unit substitutes pixel data acquired as character and/or line images in image data of input blocks with a substitution value determined based on pixel data having halftone attributes.

Abstract: A color image residue transform and/or inverse transform method and apparatus, and a color image encoding and/or decoding method and apparatus using the same are provided. The residue transform method includes: obtaining a residue corresponding to the difference of an original image and a predicted image; and transforming the residue by using a relation between residues of color image components. The residue inverse transform method includes: generating a residue for each component by performing residue inverse transform of the residue transformed original image; and restoring the original image by adding a predicted image to the residue of each component. Also, the color image lossless encoding method using the residue transform includes: obtaining a residue corresponding to the difference of an original image and a predicted image; and performing encoding by transforming the residue by using the relation between residues of predetermined components.

Abstract: Provided are a method and apparatus for interpolating an image. The method includes: selecting a first filter, from among a plurality of different filters, for interpolating between pixel values of integer pixel units, according to an interpolation location; and generating at least one pixel value of at least one fractional pixel unit by interpolating between the pixel values of the integer pixel units by using the selected first filter.

Abstract: An image signal processing apparatus, the method and a camera system are provided, by which highly efficient processing close to 1-path processing can be performed without deteriorating a picture quality or taking too much time for the processing, a capacity required for a compression rate, band and memory in the worst case can be assured and a random accessing property is not impaired when compressing image data: wherein the apparatus has at least a first signal processing unit, a second signal processing unit, and a storage unit accessed by the first signal processing unit and the second signal processing unit; wherein the first signal processing unit includes at its interface part with the storage unit a band compression expansion unit having functions of compressing input image data based on a predetermined band compression method, writing the same in the storage unit, and expands compressed data read from the storage unit.

Abstract: Wavelet transformation is performed at a plurality of levels as to image signals. A first buffer stores, independently for each of the levels, a part of coefficients from results of analysis filtering in a horizontal direction of the image signals. A second buffer stores, independently for each of the levels, a part of coefficients generated in a computation process of analysis filtering in a vertical direction of the image signals. A vertical filtering unit performs the vertical direction analysis filtering, using coefficients read out from the first and second buffers. A horizontal filtering unit performs analysis filtering in the horizontal direction, using coefficients from the results of the vertical direction analysis filtering as the input of the horizontal direction analysis filtering for the next level, except for the final level of the levels.

Abstract: Techniques are provided for compressing and decompressing image data which may reduce the distortion that may otherwise be created by the compression of data values representative of null posts, overlays or other features that differ from the underlying image. In compression, at least one coefficient generated by a forward wavelet transform may be replaced with respective replacement coefficients. The transformed image data is then subjected to an inverse wavelet transform to generate modified image data in which the data values which differ from the underlying image have been replaced by interpolated or extrapolated values. The modified image data may be compressed in accordance with wavelet-based image compression. Alternatively, wavelet image compression may be applied directly to the coefficients resulting from the modified forward wavelet transform.

Abstract: The present invention provides methods and apparatus for embedding an identifying pattern of visible speckles into the digitized image of each page of a document. A speckle is a cluster of black or white pixels. Speckles are printed as black speckles on the white paper, or conversely, as areas of missing black removed from the black text characters, called white speckles. The collective pattern of all embedded black and white speckles on a single document page is called a specklemark. A specklemark can survive contrast manipulations on photocopiers and binary rasterization done by fax scanning prior to data transmission. The random pattern of the black and white speckles visible in the digitized image of a document page can be detected automatically, and by systematically matching the detected pattern with those known to have been embedded into marked copies of a document page, a specific document copy can be identified.

Abstract: It is known to represent a square block of an image which has a maximum horizontal or vertical extension N as N vectors each representing one column or row, and encode it using an N×N discrete cosine transform matrix. We introduce a technique which transforms an input vector, or array, representing a portion of an arbitrarily-shaped object block in which the maximum horizontal or vertical extension is at most N, by adding to it additional padding elements, to produce a vector or array which can be encoded using an N×N discrete cosine transform. The padding maximises the number of transformed elements which are zero. We propose encoding arbitrarily-shaped objects based on this padding technique.