Adrian M. Ford, Relations between Image Quality and Still Image Compression, Ph.D. thesis, University of Westminster, May 1997.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....on the input pixels. Hence the input pixels cannot be used as a useful predictor of the output image size for our set of images. Also, their quantification does not take the image information quality into account and hence the information quality loss is not quantified. Our work relies on a study [45] of various objective image quality and color reproduction measures to quantify the subjective effects of lossy image compression. This study concluded that the JPEG Quality Factor is a good representation of the subjective, perceived image quality. The concept of information quality and measuring ....

....a way to control the amount of lossiness using a compression metric. The compression metric in JPEG utilizes quantization tables such that images lose least perceptible artifacts first. Hence, changing the compression metric is intuitively a good transcoding metric for JPEG images. Earlier work [45, 68, 44] confirmed that JPEG compression metrics such as JPEG Quality Factor outperformed other 52 0 20 40 60 80 100 0 20 40 60 80 100 Cumulative distribution ( Percentage of Original File Size All images (25 Q) All images (50 Q) All images (75 Q) TrueImages (25 Q) TrueImages (50 ....

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Adrian M. Ford. Relations between Image Quality and Still Image Compression. PhD thesis, University of Westminster, May 1997.

....JPEG Group s (IJG) 12] equivalent of the JPEG Quality Factor for images compressed using popular JPEG compressors from IJG, Adobe PhotoShop TM and Paint Shop Pro TM . We utilized results showing that the information quality loss directly corresponds to the change in the JPEG Quality Factor [13], 14] Next, we characterized the computational overhead and the expected change in image size for a particular transcoding. We showed that the computational requirements for a transcoding that changes the JPEG Quality Factor do not depend on the actual Quality Factor change, but on the sum of ....

Adrian M. Ford, Relations between Image Quality and Still Image Compression, Ph.D. thesis, University of Westminster, May 1997.

....expectations of the intended use for the image, a feature which is also dependent on factors such as past experience. The subjective assessment of quality also varies with the pictorial content of the test stimuli, even when image fidelity remains constant. In his Ph.D. thesis, Adrian Ford [7], tried a series of image quality and color reproduction measures to quantify the effects of lossy image compression on baseline JPEG images using the IJG software. Objective measurements such as tone reproduction, color reproduction (CIE #E # and Color Reproduction Index) resolution, sharpness ....

A. M. Ford. Relations between Image Quality and Still Image Compression. PhD thesis, University of Westminster, May 1997.

....expectations of the intended use for the image, a feature which is also dependent on factors such as past experience. The subjective assessment of quality also varies with the pictorial content of the test stimuli, even when image fidelity remains constant. In his Ph.D. thesis, Adrian Ford[4], tried a series of image quality and color reproduction measures to quantify the effects of lossy image compression on baseline JPEG images using the IJG software. Objective measurements of quality such as tone reproduction, color reproduction (CIE #E # and Color Reproduction Index) resolution, ....

Adrian M. Ford. Relations between Image Quality and Still Image Compression. PhD thesis, University of Westminster, May 1997.

....Independent JPEG Group s (IJG) 26] equivalent of the JPEG Quality Factor for images compressed using popular JPEG compressors from IJG, Adobe Photoshop and Paint Shop Pro. We utilized results showing that the information quality loss directly corresponds to the change in the JPEG Quality Factor [12, 20]. Next, we characterized the computational overhead and the expected change in image size for a particular transcoding. We showed that the computational requirements for a transcoding that changes the JPEG Quality Factor do not depend on the actual Quality Factor change, but on the sum of ....

....Han et al. 15] present an analytical framework for determining whether to transcode and how much to transcode an image. However, their quantification does not take the image information quality into account and hence the information quality loss is not quantified. Our work relies on a study [12] of various objective image quality and color reproduction measures to quantify the subjective effects of lossy image compression which concluded that the JPEG Quality Factor is a good representation of the subjective, perceived image quality. The work described in [3] gives assurance that a ....

A. M. Ford. Relations between Image Quality and Still Image Compression. PhD thesis, University of Westminster, May 1997.

.... we previously characterized the information quality tradeoffs, the computational requirements and the potential space gain of a transcoding that changes the JPEG [22] compression metric [3] It has been shown that the JPEG Quality factor parameter reflects a user s perception of image quality [6, 13]. Without such characterization, transcoding policies do not have the ability to measure information quality of an image. Hence, current systems transcode images to ad hoc Quality factor values, potentially leading to an increase in the image size for certain images. Current systems have countered ....

....Independent JPEG Group s (IJG) 15] equivalent of the JPEG Quality factor for images compressed using popular JPEG compressors from IJG, Adobe Photoshop and Paint Shop Pro. We utilized results showing that the information quality loss directly corresponds to the change in the JPEG Quality factor [6, 13]. Next, we characterize the computational overhead and the expected change in image size for a particular transcoding. We showed that the computational requirements for a transcoding that changes the JPEG Quality factor does not depend on the actual Quality factor change, but on the sum of ....

FORD, A. M. Relations between Image Quality and Still Image Compression. PhD thesis, University of Westminster, May 1997.

....earlier work [3] characterizes the information quality tradeoffs, the computational requirements and the potential size reductions for transcodings that change the JPEG [4] compression metric. It has been shown that the JPEG Quality factor parameter reflects a user s perception of image quality [5], 6] Without such characterization, transcoding policies do not have the ability to measure information quality loss of a transcoded image so it is impossible to ensure that preferred clients experience low degradation of quality. Without this characterization, current systems that attempt to ....

....Independent JPEG Group s (IJG) 10] equivalent of the JPEG Quality factor for images compressed using popular JPEG compressors from IJG, Adobe Photoshop and Paint Shop Pro. We utilized results showing that the information quality loss directly corresponds to the change in the JPEG Quality factor [5], 6] Next, we characterize the computational overhead and the expected change in image size for a particular transcoding. We show that the computational requirements for a transcoding that changes the JPEG Quality factor do not depend on the actual Quality factor change, but on the sum of ....

Adrian M. Ford, Relations between Image Quality and Still Image Compression, Ph.D. thesis, University of Westminster, May 1997.

....define a way to control the amount of lossiness using a compression metric. The compression metric utilizes quantization tables such that images lose least perceptible artifacts first. Hence, changing the compression metric is intuitively a good transcoding metric for JPEG images. Earlier work [10, 18, 9] confirmed that JPEG compression metrics such as JPEG Quality Factor outperformed other measures in 17 Figure 12: Sample GIF image with 256 unique colors that was better encoded as GIF (rather than JPEG) predicting the quality loss of an image. For our experiments, we reduce the image Quality ....

Adrian M. Ford. Relations between Image Quality and Still Image Compression. PhD thesis, University of Westminster, May 1997.

....Independent JPEG Group s (IJG) 9] equivalent of the JPEG Quality factor for images compressed using popular JPEG compressors from IJG, Adobe Photoshop and Paint Shop Pro. We utilized results showing that the information quality loss directly corresponds to the change in the JPEG Quality factor [10], 11] Next, we characterized the computational overhead and the expected change in image size for a particular transcoding. We showed that the computational requirements for a transcoding that changes the JPEG Quality factor do not depend on the actual Quality factor change, but on the sum of ....

Adrian M. Ford, Relations between Image Quality and Still Image Compression, Ph.D. thesis, University of Westminster, May 1997.

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Adrian M. Ford, Relations between Image Quality and Still Image Compression, Ph.D. thesis, University of Westminster, May 1997.

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A. M. Ford, Relations between Image Quality and Still Image Compression. PhD thesis, Univ. of Westminster, May 1997.

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