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- Acharya T.

Acharya T. - John Wiley & Sons, 2000. - 292 p.
ISBN 0-471-48422-9
Download (direct link): standardforImagecompressioncon2000.pdf
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Sequential buildup capability: The JPEG2000-compliant system can be designed to encode an image from top to bottom in a single sequential pass without the need to buffer an entire image, and hence is suitable for low-memory on-chip VLSI implementation. The line-based implementation of DWT and tiling of the images facilitates this feature.
Metadata: The extended file syntax format allows inclusion of metadata information to describe the data (image) into the compressed bitstream. For example, the JPX file format, defined in JPEG2000 Part 2: Extensions, allows any legal ICC (International Color Consortium) profile to be embedded in the file.
Image security: Although JPEG2000 does not dictate any particular image security mechanism, it is possible to introduce image security
features into a JPEG2000- compliant compressed file by inserting watermarks, fingerprints, or intellectual property rights information, or apply the steganography approach into the desired object or blocks of the images by accessing the corresponding compressed code-blocks and recompressing by introducing these image security features. In the JPEG2000 standards committee, definition of Part 8 (Secure JPEG2000) of the standard is an ongoing activity. Once finalized, Part 8 of the standard will guide the issues of image security and their implementation in a JPEG2000-compliant system.
In Figure 6.1, we have demonstrated the results of some of the capabilities of the JPEG2000 technology. The color version of Figure 6.1 is provided in the color figures page. The input image is a color image with three components (R, G, B) as shown in Figure 6.1(a). We applied three levels of DWT to decompose the image and generate the compressed bitstream with ROI encoding. The bitstream was generated by compressing the image losslessly. From the same bitstream, we decoded the image progressively until we reconstructed the original image as shown by the lossless arrow. While decoding in progressive manner, the reconstructed image is visually lossless at 5.2 bits per pixel or above as shown in Figure 6.1(b). In Figure 6.1(c), we show the random-access capability. We have accessed the compressed bits only for the code-blocks forming the subregion (or cropped version of the image) and decoded the result as shown in Figure 6.1(c). When we decode only one component (in this example we decoded G component), we get a grayscale image as shown in Figure 6.1(d). After decoding the bitstream progressively at two levels of resolution, we generate a 2:1 downscaled (horizontally and vertically) version of the image as shown in Figure 6.1(e). After decoding to 1.89 bits per pixel, we losslessly reconstructed the ROI portion of the image, but introducing artifacts in the rest of the image as shown in Figure 6.1(f). As a result, we can conclude that an image can be compressed once and the compressed bitstream can be decoded in many different ways to suit the desired requirement.
As of writing this book, the standard has 11 parts (because Part 7 has been abandoned) with each part adding new features to the core standard in Part
1. The 11 parts and their features are as follows:
• Part 1—Core Coding System [20] is now published as an International Standard ISO/IEC 15444-1:2000, and this part specifies the basic feature set and code-stream syntax for JPEG2000.
• Part 2—Extensions [21] to Part 1. This part adds a lot more features to the core coding system. These extensions are described in greater detail in Chapter 10.
Fig. 6.1 Example of capabilities of JPEG2000 technology.
• Part 3—Motion JPEG2000 [22] specifies a file format (MJ2) that contains an image sequence encoded with the JPEG2000 core coding algorithm for motion video. It is aimed at applications where high-quality frame-based compression is desired.
• Part 4—Conformance Testing [23] is now published as an International Standard (ISO/IEC 15444-4:2002). It specifies compliance-testing procedures for encoding/decoding using Part 1 of JPEG2000.
• Part 5—Reference Software [24]. In this part, two software source packages (using Java and C programming languages) are provided for the purpose of testing and validation for JPEG2000 systems implemented by the developers.
• Part 6—Compound Image File Format [25] specifies another file format (JPM) for the purpose of storing compound images. The ITU-T T.44|ISO 16485 [26] multilayer Mixed Raster Content (MRC) model is used to represent a compound image in Part 6 of JPEG2000.
• Part 7—This part has been abandoned.
• Part 8—Secure JPEG2000 (JPSEC). This part deals with security aspects for JPEG2000 applications such as encryption, watermarking, etc.
• Part 9—Interactivity Tools, APIs and Protocols (JPIP). This part defines an interactive network protocol, and it specifies tools for efficient exchange of JPEG2000 images and related metadata.
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