Abstract: An image data compression device includes a quantization part quantizing image data with a quantization step that varies based on a quantization parameter, a FIFO buffer part buffering quantized data of a plurality of frames, a coded data formation part reading out the quantized data from the FIFO buffer part asynchronously with a writing to the FIFO buffer part and generating coded data by encoding the quantized data, a rate control part controlling a data size of the coded data by changing the quantization step and a frame skip part skipping a generation process of the image data. The rate control part calculates the quantization parameter by using a predicted data size of the coded data of a previous frame which is calculated from a data size of the quantized data of the previous frame.

Abstract: An encoder, a decoder, an encoding method and a decoding method are provided. The encoder includes a reversible color transform module, a difference pulse code modulation (DPCM) intra prediction module, a quantization module, a reversible frequency transform module and an entropy coding module. The reversible color transform module performs a reversible color transform to output a transformed video signal according to an input video signal. The DPCM intra prediction module performs a DPCM intra prediction to output a least residual according to the transformed video signal. The quantization module performs a quantization operation to output a quantization coefficient according to the least residual. The reversible frequency transform module performs a reversible frequency transform to output a frequency coefficient according to the quantization coefficient. The entropy coding module performs entropy coding to output a compression bit stream according to the frequency coefficient.

Abstract: An image forming apparatus is provided with a resolution conversion unit 101 that integrates n pixels that are contiguous in the sub-scanning direction, and that determines an average value of pixel values of the n pixels as a pixel value of integrated pixels, a quantization unit 103 that quantizes the pixel value of the integrated pixels to N levels, an image analysis unit 100 that performs first judgment processing for judging whether the difference between the pixel values of the n input pixels exceeds a threshold value set in advance, and second judgment processing for judging whether a direction in which the pixel values of the n input pixels becomes greater is a forward direction of the sub-scanning direction or an opposite direction, and a pixel selection unit 104 that determines n output pixels, based on the judgment results, from a quantization result of the integrated pixels.

Abstract: A quantizer can be used to adjust the number of bits representing each sample value in a signal. Then, each received sample is allocated to one of a number of bins, with each bin corresponding to one of the possible quantizer output values. The quantizer can be used for providing a digital signal with a required number of bits, and the quantization interval can be adjusted. The quantization is performed in multiple stages. In a first stage, a received signal is compared with a first threshold value. In subsequent stages, the received signal is compared with respective threshold values, with the threshold value for each stage being calculated on the basis of the comparison result of the previous stage, and on the basis of an adjustable quantization interval. The quantized value is formed from the one-bit results from the comparison operations.

Abstract: An image compression and decompression method encodes and decodes pixel data based on a color conversion method. Based on the relationships of corresponding color components of two adjacent pixels, the corresponding color components are encoded either by a white and black modification, a down-sampling or an edge modification. Based on the relationships of encoded color components of the two adjacent pixels, the corresponding encoded color components are decoded either by an inverse white and black modification, an up-sampling or an inverse edge modification.

Abstract: An apparatus and a method of encoding/decoding an image are provided. The method includes generating a bitmap table by mapping a quantized image, that is quantized according to a predetermined bit-depth, to a map table, and setting a bitmap index corresponding to each pixel location of the quantized image with reference to the bitmap table; setting a fixed filter index corresponding to an image of each pixel of the image by analyzing local characteristics of the image; generating bitmap data by adding the filter index to the bitmap index; extracting a bitmap index, a bitmap table, and a filter index from the bitmap data; extracting an encoded image mapped to the bitmap index from the bitmap table; and filtering the extracted encoded image based on a filter corresponding to the filter index.

Abstract: The image encoder includes a block arrangement unit configured to chromatically subsample an externally input image signal and to arrange the image signal in units of a plurality of blocks, a plurality of Discrete Cosine Transform (DCT) units configured to perform DCT with respect to the image signal divided into the plurality of blocks, a plurality of quantization units configured to quantize the outputs of the plurality of DCT units, a delta modulation unit configured to perform Differential Pulse Code Modulation (DPCM) with respect to the outputs of the plurality of quantization units, a plurality of Huffman encoding units configured to encode the outputs of the delta modulation units using a Huffman encoding method, and a code connection unit configured to reconstruct the signals output from the plurality of Huffman encoding units in constant bit units and to output a compressed image signal. Since the image is encoded in parallel, it is possible to increase encoding speed.

Abstract: A method and apparatus for performing quantization during video compression, such as within an MPEG-2 encoder. Intra-quantization is particularly recited, although the teachings may be applied to inter-quantization as well. Computationally intensive portions of the quantization process are split into multiple components in response to differing execution probability. A first component is executed within each quantization iteration, and preferably is performed in parallel, such as using SIMD processing. At least one additional component, such as a second component, is serially processed in response to detecting a condition that does not arise with each loop iteration. Preferred embodiments of the invention replace division operations with a combination of multiply and shift operations, while making extended use of table lookup procedures to reduces processing overhead.

Abstract: A sequence of n coefficients is compressed by determining a cost-determined sequence of n coefficient indices represented by a cost-determined sequence of (run, index derivative) pairs under a given quantization table and run-index derivative coding distribution, wherein each sequence of (run, index derivative) pairs defines a corresponding sequence of coefficient indices such that (i) each index in the corresponding sequence of coefficient indices is a digital number, (ii) the corresponding sequence of coefficient indices includes a plurality of values including a special value, and (iii) each (run, index derivative) pair defines a run value representing a number of consecutive indices of the special value, and an index-based value derived from a value of the index following the number of consecutive indices of the special value.

Abstract: An image distribution apparatus divides image data of a single frame into a plurality of blocks, orthogonally transforms the blocks and calculates transformation coefficients, quantizes the calculated transformation coefficients, codes the quantized transformation coefficients, and distributes the coded image data. The image distribution apparatus acquires the quantized transformation coefficients, stores the acquired transformation coefficients in a storage unit, calculates differences between the transformation coefficients of a first frame and the transformation coefficients of a second frame stored in the storage unit in a unit of block, counts blocks whose difference values calculated above are equal to or greater than a predetermined value as changing blocks of the first frame, and determines that the first frame has changed when the counted number of blocks is equal to or greater than a predetermined value.

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: The present invention provides an image processing circuit capable of properly determining whether or not image data is a static image or a moving image and performing overdrive processing thereon.

Abstract: To predict a target code amount from a code amount calculated on a single quantizer scale. The present invention stores relationship information on a plurality of pieces of quantized data for prediction having different MB generated code amounts on a fixed quantizer scale (QI) as prediction curves, the relationship information indicating a relationship between a plurality of quantizer scales (Q) representing a plurality of quantizer steps and MB generated code amounts. The present invention quantizes image data on a macroblock-by-macroblock basis on the single fixed quantizer scale (QI) out of the predetermined plurality of quantizer scales (Q), thereby generating temporary quantized data, and calculates the MB generated code amount of each macroblock unit of this temporary quantized data.

Abstract: An image forming apparatus and method capable of decompressing and compressing image data. More specifically, the apparatus and method include decompressing first compressed image data, processing the decompressed image data, selecting from among a plurality of quantization tables a quantization table providing a compression ratio lower than a compression ratio of the first compressed image data, and compressing the processed image data.

Abstract: A symbol generation part serially inputs a data string of quantization data. If quantization data of non-zero coefficient is inputted, respective information on an absolute value, a zero run and a sign of the non-zero coefficient are stored in registers. When quantization data of the next non-zero coefficient is inputted, the respective information on the absolute value, the zero run and the sign stored in the registers are updated. At that time, the contents of the registers which have been stored immediately before the input are outputted as symbol data of the immediately preceding non-zero coefficient.

Abstract: A system and method for effectively performing an adaptive quantization procedure includes an energy calculator that initially determines energy values for subbands of input data. A quantizer receives initial quantization parameters that each correspond to a different respective one of the subbands. The quantizer calculates adaptive quantization parameters from the initial quantization parameters by utilizing corresponding ones of the energy values. The quantizer then utilizes the adaptive quantization parameters to generate quantized coefficients for the subbands during the adaptive quantization procedure.

Abstract: An image representation format for representing a digital image comprises: image information stored as a bitstream representing sequential image blocks, each block comprising one or more components, each component comprising one or more data units and each data unit being represented as a Huffman-coded stream of coefficients of basis functions, wherein a zeroth order coefficient is represented as a difference to the previous zeroth order coefficient of the corresponding component, and a block information table, which comprises: indicators to the first coefficient of a specified order of each image block in said bitstream, information indicating the number of bits in the bitstream between adjacent coefficients of said specified order of the image block, and the zeroth order coefficient of at least the first data unit of each component, said zeroth order coefficient being represented in a non-differential form.

Abstract: A method of reducing storage capacity needed to store a target image in a large database of images is presented. A target image is uploaded from a client system to a server system, which are connected through an Internet connection. An image index is queried to find an approximate match to the target image and to identify a most similar reference image to a processed target image stored in an image database. The difference between the target image and a raw image corresponding to the identified most similar reference image is encoded. A pointers corresponding to the processed reference image stored in the image index is updated to reflect the newly stored target image in the image index.

Abstract: This invention switches the number of bits per pixel between object types when converting code information into image data, thereby rendering one entire page at high speed while minimizing the influence on print quality. For this purpose, an apparatus analyzes received PDL data, and generates a DL (Display List) serving as a rendering unit. The apparatus determines whether the DL is a character/line image or a halftone image including a photograph image. When determining that the DL is a character/line image, the apparatus resizes the DL in accordance with the resolution of a printer engine, and renders each color component at an 8-bit precision (integer). When determining that the DL is a halftone image including a photograph image, the apparatus resizes the DL in accordance with the resolution of the printer engine, and renders each color component at a 10-bit precision (8-bit integral part+2-bit decimal part).

Abstract: A decoding apparatus includes a random-number generating section and a decoding section. The random-number generating section generates random numbers according to distribution of original data corresponding to respective quantization indexes. The decoding section generates decoded data on a basis of the random numbers generated by the random-number generating section.

Abstract: An image representation format for representing a digital image comprises: image information stored as a bitstream representing sequential image blocks, each block comprising one or more components, each component comprising one or more data units and each data unit being represented as a Huffman-coded stream of coefficients of basis functions, wherein a zeroth order coefficient is represented as a difference to the previous zeroth order coefficient of the corresponding component, and a block information table, which comprises: indicators to the first coefficient of a specified order of each image block in said bitstream, information indicating the number of bits in the bitstream between adjacent coefficients of said specified order of the image block, and the zeroth order coefficient of at least the first data unit of each component, said zeroth order coefficient being represented in a non-differential form.

Abstract: An image representation format for representing a digital image comprises: image information stored as a bitstream representing sequential image blocks, each block comprising one or more components, each component comprising one or more data units and each data unit being represented as a Huffman-coded stream of coefficients of basis functions, wherein a zeroth order coefficient is represented as a difference to the previous zeroth order coefficient of the corresponding component, and a block information table, which comprises: indicators to the first coefficient of a specified order of each image block in said bitstream, information indicating the number of bits in the bitstream between adjacent coefficients of said specified order of the image block, and the zeroth order coefficient of at least the first data unit of each component, said zeroth order coefficient being represented in a non-differential form.

Abstract: An estimation system provides quality measure of a given image for image/video applications to determine if the image needs to be enhanced or not. The system systemically measures the image quality by estimating quantization parameter of the compressed digital image. This allows estimating the image quantization parameter effectively in the pixel domain. Because block artifact are caused by image compression transforms, especially in flat image region, the estimation system first detects the suspicious regions of the image for the block artifacts by calculating a variance for each location in the image. Next, noise power is computed by using the detected regions. Then, the estimated noise power is compared with the statistical model to calculate the quantization parameter that is used in the encoder side when the input image is compressed. Finally, a quantization parameter is used as a quality measure of the input image.

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: The compression algorithm presented here is intended for the types of digital images acquired by solar system exploring spacecraft and missions, but can be utilized for all types of sequential data. It is lossy, but results in images whose Peak Signal to Noise Ratio remains in excess of 30 decibels, considered to be the threshold of being indistinguishable from the original image. Currently employed spacecraft compression algorithms are probabilistic, and are costly in terms of spacecraft weight, power, computation, memory and volume requirements. The algorithm submitted is non-probabilistic, requires less than 1 kilobyte of programming and memory space for computations, has low power and weight requirements, and can reside on a single Application Specific Integrated Circuit (ASIC), and. It processes utilizing addition and comparison only—no advanced numerical solution generation, function generation by series expansion, or other mathematical processing is required.

Abstract: The present invention provides an information processing apparatus and control method thereof and a storage medium that stores its control program capable of generating a code image with the optimum device in accordance with the amount and/or contents of the information to be encoded, and/or considering the load of the equipment. The information processing apparatus is electrically connected to an image processing apparatus, and includes: a deciding section for deciding on whether to generate a code image by encoding information or to issue a command for causing to generate the code image by encoding the information; and a processing section for generating, when the deciding section decides to generate, the code image by encoding the information and transmitting it to the image processing apparatus, and for transmitting, when the deciding section decides to issue, the command to the image processing apparatus.

Abstract: A block encoder is operable to encode a target region of an image. The encoder encodes blocks from a target region of an image. The encoded blocks are stored in a scan order of the image. The encoded blocks are reordered into a scan order for the target region, and are output as an encoded image bit stream.

Abstract: The image processing method for performing halftoning of a digital image constituted by an array of pixels having grayscale values which correspond to a content of the digital image, the method comprises the steps of: grouping the pixels constituting the digital image into a first group comprising pixels in pixel positions from which a quantization error generated through quantization is diffused to a peripheral pixel, and a second group comprising pixels in pixel positions from which the quantization error generated through quantization is not diffused to a peripheral pixel; performing a first quantization process on the pixels belonging to the first group using a threshold matrix; determining the quantization error generated during the first quantization process; diffusing the quantization error obtained in the quantization error determining step to at least one non-quantized pixel belonging to the second group which is adjacent to the pixel subjected to the first quantization process; and performing a seco

Abstract: A video encoding method comprises selecting one combination, for each block of an input video signal, from a plurality of combinations each including a predictive parameter and at least one reference picture number determined in advance for the reference picture, generating a prediction picture signal in accordance with the reference picture number and predictive parameter of the selected combination, generating a predictive error signal representing an error between the input video signal and the prediction picture signal, and encoding the predictive error signal, information of the motion vector, and index information indicating the selected combination.

Abstract: Techniques described herein are generally related to steganalysis of suspect media. Steganalysis techniques may include receiving instances of suspect media as input for steganalytic processing. A first set of quantized blocks of data elements may be identified within the media, with this first set of blocks being eligible to be embedded with steganographic data. A second set of quantized blocks of data elements may be identified within the media, with this second set of blocks being ineligible to be embedded with steganographic data. The steganalysis techniques may requantize the first and second blocks. In turn, these techniques may compare statistics resulting from requantizing the first block with statistics resulting from requantizing the second block. The steganalysis techniques may then assess whether the first block of data elements is embedded with steganographic features based on how the statistics of the second blocks compare with the statistics of the first blocks.

Abstract: A scaleable macro block rate control method particularly well-suited for MPEG video. There is provided a method to easily derive a quantization parameter (QP) value using information such as bit usage, previous QP values and SAD values from the past encoded and future frames. The method utilizes quantization estimation techniques based on statistical relationships between different intensity measures, such as distortion intensity, absolute difference intensity and mean of absolute difference intensity. The method is well-suited to applications utilizing MPEG video such as MPEG-1, MPEG-2, MPEG-4, JVT/H.264 standards and so forth.

Abstract: Method determining lookup table (“LUT”) for embedding watermark. For each quantization cell, calculating probabilities that signal point falls into cell. Selecting cell by probabilities. Setting LUT value to watermark value with largest probability, subject to run constraint. For remaining cells, repeating selecting and setting steps. Other method determining quantization ensemble by calculating probability density function for signal points where the watermark value to be embedded. Distortion and robustness functions are formulated. Given robustness or distortion is selected. Functions optimized, and ensemble of quantizers determined with parameters that comply. Other method quantizing in association with lossy compression. Strength of compression determined. Adapting strength of watermark with strength of compression by a mapping. Other method selecting points for embedding watermark. Determine threshold between large and small signal points using statistical method.

Abstract: A system and method for image and video compression and decompression using compressive sensing is provided. A method for decompressing a compressed image, where the compressed image having a plurality of compressed image blocks, and the method is performed on a processor, includes selecting a compressed image block, entropy decoding the selected compressed image block, and recovering an image block corresponding to the decoded selected compressed image block using compressive sensing recovery.

Abstract: An image processing apparatus includes a size acquiring unit that acquires a block size of an orthogonal transformation from encoded data of an image compressed by performing the orthogonal transformation and quantization for each block; a filter selecting unit that selects a filter for each block, the filter reducing an encoding distortion from each block of a decoded image; and an encoding-distortion reducing unit that reduces an encoding distortion by the filter on all pixels within the block. The filter selecting unit selects the filter so that a strength of the filter strengthens by increasing of the block size, or selects the filter so that the number of taps of the filter decreases by reduction of the block size.

Abstract: Disclosed is an image processing apparatus comprising an image compression conversion unit to quantize an image having attribute data for each pixel, wherein when a region has the attribute data of a photographic image, the image compression conversion unit quantizes the region by a BTC method, wherein when a region has the attribute data of other than the photographic image, and the region is a halftone region, the image compression conversion unit quantizes the region by the BTC method, and wherein when a region has the attribute data of other than the photographic image, and the region is a high resolution region, the image compression conversion unit generates a density pattern for the region to quantize the region according to the generated density pattern.

Abstract: A value of a selection parameter is sequentially set from among a plurality of parameters included in a modeling equation to derive a quantization matrix. A value of each of the parameters is sequentially derived based on a code amount and an encoding distortion obtained from an encoding using a quantization matrix generated from an updated parameter set.

Abstract: A reflectance image that represents a reflectance distribution, and an illuminance component image that represents an illuminance distribution are generated from an input image. A plurality of small regions, which are divided based on illuminance components of the generated illuminance component image, are specified. A quantized image is generated from the reflectance image for respective specified small regions. Regions having equal quantized pixel values are acquired in the quantized image. Representative pixel values for the respective acquired regions are acquired based on the illuminance component image. Quantized pixel values of the respective acquired regions are corrected using the acquired representative pixel values.

Abstract: A video encoding method comprises selecting one combination, for each block of an input video signal, from a plurality of combinations each including a predictive parameter and at least one reference picture number determined in advance for the reference picture, generating a prediction picture signal in accordance with the reference picture number and predictive parameter of the selected combination, generating a predictive error signal representing an error between the input video signal and the prediction picture signal, and encoding the predictive error signal, information of the motion vector, and index information indicating the selected combination.

Abstract: Methods, machines, systems and machine-readable instructions for processing an image are described. In one aspect, the image is divided into a population of image blocks. Frequency domain vectors are generated from respective ones of the image blocks. Each of the frequency domain vectors includes a respective set of values corresponding to a set of transform coefficients. Preliminary estimates of quantization parameter values are determined from frequency distributions of the transform coefficient values in a set of the frequency domain vectors corresponding to a variable sample of the population. The variable sample is determined at least in part by at least one threshold. Values of quantization parameters are estimated from the preliminary estimates.

Abstract: A video encoding method comprises selecting one combination, for each block of an input video signal, from a plurality of combinations each including a predictive parameter and at least one reference picture number determined in advance for the reference picture, generating a prediction picture signal in accordance with the reference picture number and predictive parameter of the selected combination, generating a predictive error signal representing an error between the input video signal and the prediction picture signal, and encoding the predictive error signal, information of the motion vector, and index information indicating the selected combination.

Abstract: An image encoding method and apparatus capable of improving image compression efficiency by using human psycho-visual characteristics are provided. In the image encoding method and apparatus, an image signal component of which amplitude is equal to or less than a just noticeable distortion (JND) that is a minimum limit of a visually noticeable image is not encoded according to image characteristics by using the masking effect of the human visual system (HVS), thereby improving an image compression rate without visible deterioration of image quality.

Abstract: A video encoding method comprises selecting one combination, for each block of an input video signal, from a plurality of combinations each including a predictive parameter and at least one reference picture number determined in advance for the reference picture, generating a prediction picture signal in accordance with the reference picture number and predictive parameter of the selected combination, generating a predictive error signal representing an error between the input video signal and the prediction picture signal, and encoding the predictive error signal, information of the motion vector, and index information indicating the selected combination.

Abstract: A video encoding method comprises selecting one combination, for each block of an input video signal, from a plurality of combinations each including a predictive parameter and at least one reference picture number determined in advance for the reference picture, generating a prediction picture signal in accordance with the reference picture number and predictive parameter of the selected combination, generating a predictive error signal representing an error between the input video signal and the prediction picture signal, and encoding the predictive error signal, information of the motion vector, and index information indicating the selected combination.

Abstract: Described herein is a method and system for video classification. The method and system can use predetermined color ranges to classify a video block. On a relative basis, a greater number of bits can be allocated to perceptually important video data such as skin. The quantization is adjusted accordingly. Determining relative quantization shifts for macroblocks in a picture prior to video encoding enables a corresponding bit allocation that can improve the tradeoff between perceptual quality and bit rate.

Abstract: The invention relates to a method for coding N+1 images comprising a step of temporal analysis of these images generating a low-frequency image and N high-frequency images. It furthermore comprises the following steps: dividing each of the N+1 low-frequency and high-frequency images into N+1 parts; interleaving the N+1 low-frequency and high-frequency images so as to generate N+1 interleaved images and so that the N+1 parts of the low-frequency image are distributed between the N+1 interleaved images, each of the N+1 interleaved images comprising a single part of the low-frequency image; and coding the N+1 interleaved images independently of one another, each of the interleaved images being coded with one and the same number of bits.

Abstract: An image processing method for executing a quantization process of image data by error diffusion, executes a step of generating first image data by adding a quantization error to input image data, a step of generating second image data by quantizing the first image data by comparing the first image data with a predetermined threshold value, a step of generating third image data by dequantizing the second image data, a calculation step of calculating a quantization error for each pixel on the basis of the difference between the first and third image data, a storage step of storing information indicating a positive/negative sign of the calculated quantization error for a predetermined number of pixels in a storage unit, and a correction value generation step of generating a correction value used to correct at least one of the first image data and the threshold value on the basis of the information which is stored in the storage unit and indicates the positive/negative sign.

Abstract: Systems, methods and media for managing an interactive streaming image system are disclosed. More particularly, hardware and/or software for generating, encoding, and transmitting image frames to an interactive client are disclosed. One embodiment provides a method for streaming images from a server to a client. Embodiments may include receiving from the client via a network client information and generating a new image frame based on the received client information. Embodiments may also include comparing the new image frame and a previous image frame and setting a new compression level based on the comparison between the new image frame and the previous image frame. Embodiments may also include encoding the new image frame based on the new compression level and transmitting the encoded new image frame and an indication of the new compression level to the client via the network.

Abstract: Systems and methods for block-based fast image compression are described. In one aspect, a digital image is segmented into multiple blocks. A respective set of statistical characteristics is identified for each of the segmented blocks. Each of the blocks is encoded with a particular encoding algorithm of multiple encoding algorithms. The particular encoding algorithm that is used to encode a particular block segmented from the digital image is selected to efficiently encode the block in view of statistical characteristics associated with the block. Thus, blocks of different block types may be encoded with different encoding algorithms.

Abstract: A decoding apparatus is provided which can perform error concealment accurately by reducing false detection of an error and detecting an error efficiently. The decoding apparatus (100) which decodes a coded image coded on a per-block basis, includes: a variable length decoding unit (101) that decodes a coded image; an error occurrence position detection unit (109) that determines a candidate block on which an error has possibly occurred, by using a quantization parameter which is obtained for each block and which is resulting from the decoding by the variable length decoding unit (101); and an error correction unit (110) that corrects blocks including and following the candidate block determined by the error occurrence position detection unit (109).

Abstract: A processor performs layout analysis, and classifies pieces of bitmap data into a character area and a picture area. The processor divides each of the character area and the picture area into a plurality of tiles having a predetermined shape, thereby creating a table including information representing either character attribute or picture attribute in association with each tile number. The processor performs scalar quantization for data of each tile using a quantization coefficient for characters or pictures, based on the created table. The processor encodes the data of each tile using an SNR progressive technique or a resolution progressive technique, and performs post quantization for the data using a quantization parameter for characters or pictures. Then, the processor stores the encoded data into a storage device.