Modified Huffman Code Research Articles

Colour filter array demosaicking over compression through modified grey wolf optimization technique

ABSTRACTThe three colour intensity values red, green and blue are acquired in a single pixel on using a multi-sensor camera. The single sensor camera uses the colour filter array to grab only one intensity value in a pixel location. The reconstruction of the so-called raw image into a full colour image is called demosaicking. This paper proposes a novel framework for effective demosaicking combined with the compression over the input image using a modified grey wolf optimization algorithm. The demosaicking process is efficient in applying the Modified Grey Wolf Optimized wavelet compression to optimally select the coefficients and Modified Huffman Coding technique to the image before demosaicking. The proposed technique is evaluated by the Peak Signal Noise Ratio, Structural Similarity Index Measure and Feature Similarity Index Measure values and has proved both subjectively and objectively to have better demosaicking results.

Implementation of Modified Huffman Coding in Wireless Sensor Networks

Implementation of Modified Huffman Coding in Wireless Sensor Networks

A LOSSLESS COLOR IMAGE COMPRESSION USING AN IMPROVED REVERSIBLE COLOR TRANSFORM WITH HIERARCHICAL PREDICTION AND MODIFIED HUFFMAN CODING

In case of the conventional lossless color image compression methods, the pixels are interleaved from each color component, and they are predicted and finally encoded. In this paper, we propose a lossless color image compression method using hierarchical prediction of chrominance channel pixels and encoded with modified Huffman coding. An input image is chosen and the R, G and B color channel is transform into YCuCv color space using an improved reversible color transform. After that a conventional lossless image coder like CALIC is used to compress the luminance channel Y. The chrominance channel Cu and Cv are encoded with hierarchical decomposition and directional prediction. The effective context modeling for prediction residual is adopted finally. It is seen from the experimental result the proposed method improves the compression performance than the existing method.

Image Compression Using Modified Huffman Coding

Image compression using modified Huffman coding can be obtained by dividing the original grey level image into unoverlapped blocks and setting homogeneity criterion to test each block individually depending on a threshold value and the well-known techniques of Quad-tree decomposition. By taking threshold value as 0.2, Huffman coding for encoding and decoding of the image are the techniques which have been applied for the compression of satellite imageries. The results indicate that for a Lena image, CR is 9.79 and PSNR value is 24.96, Satellite image values are 12.69 and 25.01, respectively. The noise used is salt and pepper, and it is filtered by wellknown technique of Wiener filter. The results are presented and discussed in this paper.

Hybrid Algorithm for Lossless Image Compression using Simple Selective Scan order with Bit Plane Slicing

Problem statement: Identifying the new lossless image compression algorithm for high performance applications like medical and satellite imaging; a high quality lossless image is most important when reproduction which leads to classify the data for decision making. Approach: A new lossless hybrid algorithm based on simple selective scan order with Bit Plane Slicing method is presented for lossless Image compression of limited bits/pixel images, such as medical images, satellite images and other still images common in the world. Efficient coding is achieved by run length and modified Huffman coding. This approach is combined with efficient selective scan order for entire image in one pass through. Results: The new hybrid algorithm achieves good compression rate, compared to the existing schemes of coding with different test images. Conclusion: Compared to the existing standards JPEG-LS and CALIC, the compression rate is reduced with our proposed algorithm for different standard test images.

A new data hiding strategy with restricted region protection

This paper proposes a novel data hiding scheme that aims to prevent certain regions from modifying. These regions are specified by users, and a location map is generated to indicate where the changeable pixels are located. To reduce the size of this extra information, the location map is compressed using modified Huffman coding, and the compressed code is embedded into cover images. The Huffman code and the secret information can be separated automatically during the extracting procedure, without knowing the size of the compressed code in advance. The experimental results show that our proposed scheme has flexibility in data hiding capacity and stego image quality control, and the regions can be preserved well. Thus, the proposed scheme can be applied to a wide variety of applications.

An efficient test vector compression scheme using selective huffman coding

This paper presents a compression/decompression scheme based on selective Huffman coding for reducing the amount of test data that must be stored on a tester and transferred to each core in a system-on-a-chip (SOC) during manufacturing test. The test data bandwidth between the tester and the SOC is a bottleneck that can result in long test times when testing complex SOCs that contain many cores. In the proposed scheme, the test vectors for the SOC are stored in compressed form in the tester memory and transferred to the chip where they are decompressed and applied to the cores. A small amount of on-chip circuitry is used to decompress the test vectors. Given the set of test vectors for a core, a modified Huffman code is carefully selected so that it satisfies certain properties. These properties guarantee that the codewords can be decoded by a simple pipelined decoder (placed at the serial input of the core's scan chain) that requires very small area. Results indicate that the proposed scheme can provide test data compression nearly equal to that of an optimum Huffman code with much less area overhead for the decoder.

Arabic-document compression: A close look at group 3 international digital facsimile coding standards

Efficient bit-representation or compression of documents is an important issue in many applications. The amount of compression depends on the document contents such as written scripts, diagrams, tables, etc. The contents of the document determine the limit of this compression. In the CCITT Recommendation T.4, ‘Standardization of group 3 apparatus for document transmission’, a modified Huffman code was chosen as the standard compression technique [1]. The selection is based on examining documents with contents of different natures. With the cursive nature and the domination of certain shapes in printed Arabic, one may be curious to know the compression efficiency of the chosen standard for documents with printed Arabic contents. For this purpose, more than ten documents containing printed Arabic script have been scanned and analyzed in this paper. Both the entropy, based on the Capon model [5], and the compression rates using the modified Huffman code are calculated. Our results show that the CCITT coding standard seems to be robust for documents with printed Arabic script.

Efficient hardware decoding method for modified Huffman code

A hardware decoder using an efficient decoding method for the modified Huffman code is illustrated. The decoding method can be realised by simple hardware thus enabling the whole data compression unit to be incorporated as a peripheral device for a microcontroller.

An encoding procedure and a decoding procedure for a new modified Huffman code

The conventional Huffman table, which stores a set of code words with different lengths, is difficult to construct. An easily constructed table that includes a code-length array and an encoding mapping array can accompany an encoding procedure to replace the conventional Huffman table. The code-length array records the number of code words of the same length, and the index of this array represents the code length. The encoding mapping array records the indexes of the probability vector for the corresponding symbols, with the elements of the probability vector in decreasing order. The code word generated by the encoding procedure is a new modified Huffman code that can be decoded by a simple procedure. The hardware structure for the encoding and decoding procedures is presented. The required maximum number of clock cycles for encoding and decoding are (N+1) and (N+2), respectively, where N is the number of symbols in the source alphabet. The encoding procedure can accompany the generation of the code-length array, replacing many Huffman tables required in the coding system with a time-varying probability vector. The algorithm has a good performance with respect to speed and memory requirements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Algorithm for Construction of Variable Length Code with Limited Maximum Word Length

As a high efficiency coding method for TV signals, variable length coding, such as Huffman coding, is extremely effective. However, when this variable length coding is applied to an actual TV codec which requires high-speed real-time processing, maximum word length will be limited for the hardware configuration. This correspondence describes an algorithm for the construction of a modified Huffman code with limited maximum word length by means of a "top-down" procedure meeting this requirement instead of the conventional "bottom-up" algorithm.

Error Sensitivity of CCITT Standard Facsimile Coding Techniques

The CCITT has defined Group 3 facsimile apparatus as that which digitally transmits an ISO A4 document over a switched telephone circuit in approximately one minute. Data compression is employed to achieve the reduced transmission time. Study Group XIV of the CCITT has drafted Recommendation T.4 to achieve compatibility between Group 3 facsimile devices. The standard data compression technique specified by T.4 is a one-dimensional coding scheme in which runlengths are encoded using a modified Huffman code (MHC). The recommendation also includes an optional twodimensional compression technique known as the modified READ code (MRC). It is recognized that the switched telephone network is prone to error when transmitting digital data at the standard T.4 data rate of 4800 bits/s. This paper evaluates the error sensitivity of the MHC and MRC when operating over a typical telephone circuit. The error sensitivity analysis is accomplished by means of computer simulation. The error performance of the two coding techniques is analyzed both quantitatively and qualitatively. The quantitative analysis is accomplished using the error sensitivity factor which represents the average number of incorrect pels in the output document caused by a transmission error. The qualitative analysis is based upon viewing actual error-contaminated images generated in the simulation process. Two separate analyses have been performed. First, error sensitivity data for both the MHC and MRC are developed under identical operational conditions, and their relative performance is discussed. In the second part four different techniques for processing the received facsimile signal (MRC), to minimize the subjective effect of transmission errors, are analyzed.

Adaptive Block/Location Coding of Facsimile Signals Using Subsampling and Interpolation for Pre- and Postprocessing

In this paper, an information lossy preprocessing technique using subsampling is described. Notches and pinholes in the original image are first removed using a set of masks, after which single element runs are doubled to preserve connectivity. The image is then subsampled by taking alternate picture elements (pels) horizontally and vertically. Enlargement of the subsampled image is carried out at the receiver where replication, bilinear, and cubic B-spline interpolation techniques are investigated. The edges of the interpolated images are "smoothed out" by a set of restoration masks, producing a visually acceptable result. A formal subjective experiment is also conducted to determine the order of subjective preference of the resulting restored images. Finally, adaptive block/ location coding (ABLC), with respect to a numerical measure of complexity, is used to code the subsampled image. Compression ratios achieved for the CCITT documents range from 13.31:1 to 63.77:1, a reduction, on average, by about 40 percent when one-dimensional run-length coding using the modified Huffman code (MHC) is applied to the subsampled image and by about 73 percent when MHC is applied to the original data.

International digital facsimile coding standards

Recently Study Group XIV of CCITT has drafted a new Recommendation (T.4) with the aim of achieving compatibility between digital facsimile apparatus connected to general switched telephone networks. A one-dimensional coding scheme is used in which run lengths are encoded using a modified Huffman code. This allows typical A4 size documents in the form of black and white images scanned at normal resolution (3.85 lines/mm, 1728 pels/line) to be transmitted in an average time of about a minute at a rate of 4800 bit/s. The Recommendation also includes a two-dimensional code, known as the modified relative element address designate (READ) code, which is in the form of an optional extension to the one-dimensional code. This extension allows typical documents scanned at high (twice normal) resolution (with every fourth line one dimensionally coded) to be transmitted in an average time of about 75 s at 4800 bit/s. This paper describes the coding schemes in detail and discusses the factors which led to their choice. In addition, this paper assesses the performance of the codes, particularly in relation to their compression efficiency and vulnerability to transmission errors, making use of 8 CCITT reference documents.

Adaptive pel location coding for bilevel facsimile signals

An adaptive pel location coding scheme is proposed for document encoding. Operating in one or two dimensions, it achieves high compression ratios at the expense of slight image degradation. Comparison with autoadaptive block coding, run-length coding using the B1 code, and modified Huffman coding are presented.

An Ordering Scheme for Facsimile Coding

We give simulation results using one of our ordering algorithms for the coding of eight ccitt test documents. These algorithms do not make any approximations and therefore can reproduce the documents exactly at the receiver. The code design is similar to the one-dimensional modified Huffman code that has been proposed by the ccitt as a standard. One-dimensional run-length coding using the modified Huffman code results in 446,316 bits per document on the average, which can be transmitted in 92.77 seconds using a transmission rate of 4800 bits per second. Our ordering algorithm, which is two-dimensional in nature, requires, on the average, 264,632 bits per document, or 55.13 seconds per document for the same transmission rate. Thus, the ordering scheme reduces the transmission time by approximately 41 percent, compared to one-dimensional run-length coding.