A Quick Illustration of JPEG 2000Fall 2003 ECE533 Final Project ProposalDepartment of Electrical and Computer EngineeringUniversity of Wisconsin-MadisonBy_______________ _______________ Kim-Huei Low Data FokSubmitted to: Professor HuDec 12th 20031. IntroductionThe international JPEG (Joint Bi-level Image Experts Group) and JBIG (Joint Photographic Experts Group) groups,who represent a wide variety of companies and academic institutions worldwide, have created a new image codingsystem that uses state-of-the-art compression techniques based on wavelet technology. This standard is called theJPEG 2000, which its architecture should lend itself to a wide range of uses from portable digital cameras through toadvanced pre-press, medical imaging and other key sectors.The JPEG 2000 standard has 11 parts [2], in which part 1, the core coding system is now published as anInternational Standard. Parts 2-6 are complete or nearly complete, and parts 8-11 are still under development. A Javasoftware implementation of the standard (JJ2000) is also found [1], which implements the entire part 1 of thestandard.Although both the standard and the tools are available to the public, but due to the complexity of the standards,especially for amateurs who just begin to learn about image coding, we feel that there is a need to present a quicktutorial of JPEG 2000. This paper is therefore written to give new users a grasp of JPEG 2000.2. ApproachThe most straightforward way to present a quick tutorial of JPEG 2000 is to illustrate and to examine its features oneby one in great details. In order to do that, we have familiarized ourselves with the standards and the tools. At first,we have difficulties understanding some of the algorithms and specifications in the standard. However, after severaliterations of reading and with the help of the Java tool set, we are able to Figure out all the features in JPEG 2000.Similar to the JPEG 2000 final committee draft, we will present our work in the same order. We will briefly explaineach section of the standard, illustrate each feature, discuss about its applications, and list the pros and cons. Forvisualization purposes, most of the time, we encode images with extremely low bit rate to show noticeabledifferences even with small display images. The encoding bit rates are tuned with very fine granularity, base on thefeature that we are illustrating.3. Experiments, Results & DiscussionsAnnex A, Annex C and Annex D of the JPEG 2000 standard will not be examined. This is because these sections donot consist of a feature. Instead, Annex A talks about the headers and markers which is simply a bunch of constantsthat are used to efficiently represent an image. Although it is essential to understand Annex C (Arithmetic EntropyCoding) and Annex D (Coefficient Bit Modeling), however, to a user, these are basically the algorithms. Featurewise, they do not play an important role.3.1 Annex B: Data Ordering3.1.1 Tile divisionIn JPEG 2000, an image offset and a tile offset is often given to specify the upper left corner of the desired croppedimage. It’s expensive to load a huge image in hardware and try to encode it. Therefore, images are typically brokendown into multiple tiles, and encoded independently. The Discrete Wavelet Transformation (DWT) is designed forthis purpose.A tile-component is a tile consists of only one component. For example, a RGB image would be broken down into Rtile-component, G tile-component and B tile-component. Each tile-component is then further divided down todifferent resolutions and sub-bands with the use of DWT. Each resolution is divided into multiple precincts whichidentify a geometric position of a tile-component of an image. Furthermore, each sub-band at each resolution isdivided into multiple code-blocks, which will be coded into individual packets.Shown below is an illustration of the selection of code-blocks for encoding, assuming only two levels of DWTdecomposition. Due to the cropping of a tile-component, not all precinct partitions and code-blocks are included forcoding. A precinct is only included if the entire precinct falls within the cropped region of the tile-component.Moreover, only code-blocks that are overlapped with the designated precincts are included for coding as shown inFigure 3.1.1-4. Figure 3.1.1-1: Original DWT Figure 3.1.1-2: Precinct Selection Figure 3.1.1-3: Sub-band Selection Figure 3.1.1-4: Code-block Selection3.1.2 Progression OrderFor a given tile, the packets contain data from a specific layer, a specific component, a specific resolution, and aspecific precinct. The order in which these packets are interleaved is called the progression order. The interleavingof the packets can progress along four axes: layer, component, resolution and precinct.As shown below, progression in layer and resolution results in sharper image when bit rate increases, andprogression in precinct results in overall clearer image, as more precincts/portions of the image are decoded. We alsoshow that progression in component results in less color distortion and increasing contrast as more components aredecoded.There are altogether 5 progression types defined in the JPEG 2000 standard. They are listed below:1) Layer-Resolution-Component-Position Progressive- All positions are encoded before all components before all resolutions before all layers.- Image quality is reduced before any color components or parts of the image being thrown away.2) Resolution-Layer-Component-Position Progressive- Visually same effects as Layer-Resolution-Component-Position Progressive.3) Resolution-Position-Component-Layer Progressive- In general, same effects as Layer-Resolution-Component-Position Progressive.- Better quality since layer has the highest priority to be coded, trading off some portions of the image.4) Position-Component-Resolution-Layer Progressive- All layers are encoded before all resolutions before all components before all positions.- Results in loss of parts of image as positions are truncated to achieve the target bit rate.5) Component-Position-Resolution-Layer Progressive- Identical to Position-Component-Resolution-Layer Progressive- Loss of color components occurs before any parts of the image are truncated.For illustration, we have grouped these progression types into
View Full Document
Unlocking...