Improvements to JPEG-LS via diagonal edge-based prediction

JPEG-LS is the latest pixel based lossless to near lossless still image coding standard introduced by the Joint Photographic Experts Group (JPEG) '. In this standard simple localized edge detection techniques are used in order to determine the predictive value of each pixel. These edge detection techniques only detect horizontal and vertical edges and the corresponding predictors have only been optimized for the accurate prediction of pixels in the locality of horizontal and/or vertical edges. As a result JPEG-LS produces large prediction enors in the locality of diagonal edges. In this paper we propose a low complexity, low cost technique that accurately detects diagonal edges and predicts the value of pixels to be encoded based on the gradients available within the standard predictive template of JPEG-LS. We provide experimental results to show that the proposed technique outperforms JPEG-LS in terms of predicted mean squared error, by a margin ofup to 8.5 1%

Lossless Compression of Color Palette Images with One-Dimensional Techniques

Palette images are widely used on the World Wide Web (WWW) and in game-cartridge applications. Many images used on the WWW are stored and transmitted after they are compressed losslessly with the standard graphics interchange format (GIF), or portable network graphics (PNG). Well-known 2-D compression schemes, such as JPEG-LS and JPEG-2000, fail to yield better compression than GIF or PNG due to the fact that the pixel values represent indices that point to color values in a look-up table. To improve the compression performance of JPEG-LS and JPEG-2000 techniques, several researchers have proposed various reindexing algorithms. We investigate various compression techniques for color palette images. We propose a new technique comprised of a traveling salesman problem (TSP)-based reindexing scheme, Burrows-Wheeler transformation, and inversion ranks. We show that the proposed technique yields better compression gain on average than all the other 1-D compressors and the reindexing schemes that utilize JPEG-LS or JPEG-2000

Hardware Implementation of JPEG-LS codec

The primary goal of this thesis is to implement a hardware version of the JPEG-LS, or JPEGLossless, image compression algorithm in VHDL. The JPEG-LS algorithm is currently the designated standard for lossless compression of grayscale and color images by the JPEG committee. Although lossy image compression is widely used when dealing with grayscale images, there are some applications that require lossless image compression so that the original image may be recovered. This is often the case for historical and legal document image archives, medical and satellite imagery, and biometric images. The JPEG-LS algorithm is much less complex than other current lossless image compression algorithms and offers similar or better compression gains. Near-lossless compression offers higher compression gains by using a pixel tolerance specified by the user. The algorithm uses a predictive technique for compression, and the resulting prediction error is encoded, not the pixel value itself. This prediction error is encoded with Golomb-Rice coding, which is optimal for a geometric distribution such as prediction error. The predictor enters a special run-length mode to encode pixels with identical values in lossless mode (or nearly identical values within a known value in near-lossless mode), which maximizes compression further. In this thesis, the JPEG-LS algorithm is implemented in C, VHDL, and further synthesized using the Synopsys synthesis tool suite. Pictorial, document, medical, remote sensing, and biometric images are used for testing the project against another standard-compliant software implementation. The compression ratio for lossless compression is approximately 2 and is greater for near-lossless compression. The end result is a Synopsys schematic that represents a JPEG-LS codec, which is capable of lossless and near-lossless encoding and decoding. Performance characteristics such as chip area, speed, and power consumption are extracted from the synthesis tool. These are approximately 375,000 gates, a 15 ns clock cycle, and 59 mW respectively. A hardware implementation of this algorithm on an FPGA or ASIC would give a digital camera or scanner an edge in the marketplace

Rate-controlled, region-of-interest-based image coding with JPEG-LS

Since the standardization of JPEG-LS, several improvements and variations to the original algorithms have been proposed. In this paper we propose a Region of Interest (ROT) based coding strategy for JPEG-LS that has the additional ability of providing effective rate controlled image compression. Given a single ROT or multiple ROTs of a fixed or arbitrary shape, the scheme we propose is able to compress a given image by a required ratio, whilst maintaining the subjective image of the ROTs at either lossless or at a quality specified by a Target Compression Ratio ( TCR) of the ROT. We provide experimental results to compare the performance of the proposed rate-control algorithm with the state of the art near lossless rate control schemes. We show that the proposed scheme is able to achieve much higher TCRs, at increased accuracy and better objective image quality, using a less computationally intensive rate control algorithm. Finally we demonstrate that the proposed ROT based coding scheme can be used to extend the applicability of JPEG-LS to medical and satellite imaging applications and provides a useful alternative to JPEG-2000 based ROT coding

A just noticeable distortion based perceptually lossless image compression codec

In this study thesis a JND (Just-Noticeable-Distortion)-Measurement will be implemented on top of JPEG-LS while only considering a grayscale bit depth of 8 Bit. This is sufficient to show a proof of concept of combining the JND approach with JPEG-LS. JPEG-LS is a widely used and relatively simple coding mechanism for lossless and near-lossless image compression. The JND measurement will be defined, implemented and integrated into JPEG-LS. Therefore a modified approach of [CL95] will be used. The quantization step size (QSS) will be adapted dynamically according to the JND value so that the compression ratio compared to a standard JPEG-LS implementation can be improved. By that, a near-lossless variable bit-rate (VBR) is introduced into the coding flow. The encoder and decoder are implemented in MATLAB and after defining the visual quality criteria the results are evaluated and analysed in matter of compression quality and performance. Two test picture sets are used and the perceptual quality of the codec will be evaluated by an Mean-Opinion-Score (MOS) test and Multi-Scale Structural Similarity (MS-SSIM) test

Extending JPEG-LS for low-complexity scalable video coding

JPEG-LS, the well-known international standard for lossless and near-lossless image compression, was originally designed for non-scalable applications. In this paper we propose a scalable modification of JPEG-LS and compare it with the leading image and video coding standards JPEG2000 and H.264/SVC intra for low-complexity constraints of some wireless video applications including graphics

Digital recording of performing arts: formats and conversion

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