Rajan L. Joshi

An overview of the JPEG 2000 still image compression standard

Abstract In 1996, the JPEG committee began to investigate possibilities for a new still image compression standard to serve current and future applications. This initiative, which was named JPEG 2000, has resulted in a comprehensive standard (ISO 15444∣ITU-T Recommendation T.800) that is being issued in six parts. Part 1, in the same vein as the JPEG baseline system, is aimed at minimal complexity and maximal interchange and was issued as an International Standard at the end of 2000. Parts 2–6 define extensions to both the compression technology and the file format and are currently in various stages of development. In this paper, a technical description of Part 1 of the JPEG 2000 standard is provided, and the rationale behind the selected technologies is explained. Although the JPEG 2000 standard only specifies the decoder and the codesteam syntax, the discussion will span both encoder and decoder issues to provide a better understanding of the standard in various applications.

Comparison of multiple compression cycle performance for JPEG and JPEG 2000

Ideally, when the same set of compression parameters are used, it is desirable for a compression algorithm to be idempotent to multiple cycles of compression and decompression. However, this condition is generally not satisfied for most images and compression settings of interest. Furthermore, if the image undergoes cropping before recompression, there is a severe degradation in image quality. In this paper we compare the multiple compression cycle performance of JPEG and JPEG2000. The performance is compared for different quantization tables (shaped or flat) and a variety of bit rates, with or without cropping. It is shown that in the absence of clipping errors, it is possible to derive conditions on the quantization tables under which the image is idempotent to repeated compression cycles. Simulation results show that when images have the same mean squared error (MSE) after the first compression cycle, there are situations in which the images compressed with JPEG2000 can degrade more rapidly compared to JPEG in subsequent compression cycles. Also, the multiple compression cycle performance of JPEG2000 depends on the specific choice of wavelet filters. Finally, we observe that in the presence of cropping, JPEG2000 is clearly superior to JPEG. Also, when it is anticipated that the images will be cropped between compression cycles when using JPEG2000, it is recommended that the canvas system be used.

On-demand rendering of an oblique slice through 3D volumetric data using JPEG2000 client-server framework

In medical imaging, the popularity of image capture modalities such as multislice CT and MRI is resulting in an exponential increase in the amount of volumetric data that needs to be archived and transmitted. At the same time, the increased data is taxing the interpretation capabilities of radiologists. One of the workflow strategies recommended for radiologists to overcome the data overload is the use of volumetric navigation. This allows the radiologist to seek a series of oblique slices through the data. However, it might be inconvenient for a radiologist to wait until all the slices are transferred from the PACS server to a client, such as a diagnostic workstation. To overcome this problem, we propose a client-server architecture based on JPEG2000 and JPEG2000 Interactive Protocol (JPIP) for rendering oblique slices through 3D volumetric data stored remotely at a server. The client uses the JPIP protocol for obtaining JPEG2000 compressed data from the server on an as needed basis. In JPEG2000, the image pixels are wavelet-transformed and the wavelet coefficients are grouped into precincts. Based on the positioning of the oblique slice, compressed data from only certain precincts is needed to render the slice. The client communicates this information to the server so that the server can transmit only relevant compressed data. We also discuss the use of caching on the client side for further reduction in bandwidth requirements. Finally, we present simulation results to quantify the bandwidth savings for rendering a series of oblique slices.

Efficient transcoding of JPEG2000 images

One of the key properties of the JPEG2000 standard is that it is possible to parse a JPEG2000 bit-stream to extract a lower resolution and/or quality image without having to perform dequantization and requantization. This property is especially useful given the variety of devices with vastly differing bandwidth and display capabilities that can now access the Internet. It is anticipated that a high-resolution JPEG2000-compressed image stored at an image server will be accessed by a variety of clients with differing needs for resolution and image quality. To satisfy the needs of these heterogeneous clients, it is essential that the server have the ability to transcode a JPEG2000 image in an efficient manner with very little loss in image quality. In this paper, we present a number of methods for transcoding a JPEG2000 image and evaluate each with respect to computational complexity and the quality of the transcoded image.