Research on image compression technology based on Huffman coding

Abstract

With the development of information technology, image has become the mainstream of information transmission. Compared with character, image contains more information, but because image and character need more storage capacity, it will occupy more bandwidth in network transmission. In order to transmit image information more quickly, image compression is a good choice. This paper is based on an eye of image compression. The method of image compression in this paper is that firstly, the image is filtered by wavelet transform to remove the redundant information in the image, and then the Huffman method is used to encode the image. The simulation results of JPEG format image show that the size of the image can be reduced in the same image effect.

Introduction

The development of modern computers, especially multimedia computer systems, has become a mainstream direction. Especially in current computer applications, many videos and audios have taken the form of digitization, leading to a large amount of data storage. However, the current development of science and technology is limited, and many hardware technologies cannot fully satisfy the requirements of computer storage resources, and the gap between the bandwidth and the bandwidth is still large [1], so the data must be compressed before the data storage and transmission, otherwise the storage and transfer of the computer system cannot be effectively carried out. Due to the existence of encoding redundancy, redundancy between pixels, and visual information redundancy in multimedia data, the original data can be compressed. Data compression technology is actually a series of re-encoding of the original data, eliminating redundant data in the original data, reducing the amount of data to a minimum, so as to achieve the purpose of compressing various media data such as images, audio, and video [2].

At present, common multimedia compression methods are divided into lossless compression methods and lossy compression methods [3]. Lossless compression compresses redundant parts of the original data. Using lossless compression, the original data can be completely recovered without any errors or distortions, that is, after compression and decompression, a copy of the original data is generated. Its compression ratio is generally 2:1–5:1. As the typical Double Space technology, the compression ratio of various types of data and files on the hard disk is about 2:1. Due to the limitation of the compression ratio, the use of lossless compression alone cannot handle the storage and transmission problems of digital sound and video images in real time. Lossy compression is at the expense of certain information, so that a higher compression ratio can be achieved [4]. The lossy compression method is mostly used for images with higher pixels, video, or sound quality files. For this type of data compression, the compression ratio can be increased by tens or hundreds of times. Most image compression methods can take this approach, mainly JPEG, MPFG and other types of files. The common coding methods used in lossy compression are predictive coding and transform coding, which allow information to be lost in the compression process. Although all data cannot be fully recovered after decompression, but the lost part of the image, whether the original image or the sound, has little effect on the understanding of the whole file, it can obtain a good compression ratio [5].

In order to make products of different manufacturers compatible, all countries have attached great importance to the establishment of universal data compression standards. Currently, three data compression coding standards commonly used in multimedia systems are [6]: ① JPEG standard (ISO CD 10918) for digital compression coding of continuous-tone still images; ② MPEG standard (ISO/IEC 11172), suitable for compression coding of moving pictures and accompanying sounds on digital storage media; ➂ CCITTH.261 standard, suitable for digital compression coding in application systems such as video telephony and conference television. At present, with the rapid development of the network, the diverse needs of users, such as the real-time transmission of streaming media, the compression and transmission of high resolution images, are largely dependent on the multimedia compression technology. The current image data compression technology cannot meet the needs of all kinds of network multimedia applications. Therefore, the research and application of multimedia technology in network transmission has become more and more active and attracted much attention, especially the focus of image data compression. JPEG2000 is the latest achievement of image compression technology in this form. JPEG2000 can facilitate progressive transmission, JPEG200O support lossy compression, also support lossless compression, good low bit rate compression performance and the protection of image security through watermark, markup, killings and encryption. It has been widely used in image compression on the network. Based on the JPEG2000 standard, this paper proposes a JPEG2000 compression method based on wavelet transform, which can well overcome the “square” effect caused by DCT transform in the JPEG. Finally, compare the JPEG2000 of this paper with the compression effect of JPEG standard and JPEG2000 standard respectively.