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William T. Plummer
01/20/2008 These comments address the several technologies originated by Massimo Ballerini (RGBLight ltd) for "enhancement and compression" of still and video digital images Within the material presented I have identified a means of lossless compression, a means of lossy compression, and at least three technologies that may be useful in enhancing digital images. Compression: Lossless Compression. The lossless compression method, called the “New Byte Representation”, uses a change in mathematical representation to improve on conventional methods of lossless compression. Conventionally, lossless compression identifies sequences of unchanging values in the color magnitudes within a stream of pixels, and replaces the repeating individual magnitudes with a simple statement of the number of subsequent pixels that repeat that magnitude. What Massimo Ballerini has done is to increase the amount of redundancy available for this type of compression by partitioning each color magnitude into at least one “coarse” part and at least one “fine” part, to be dealt with separately. In most photographs there will be longer sequences of unchanging coarse parts, and this increased redundancy has been exploited to provide a greater factor of lossless compression. Lossy Compression. The lossy compression method, called the “Dark Method”, offers a larger compression ratio than the lossless method, by sacrificing some of the information in an original digital photograph or video stream. Unlike lossless compression, in which every compression method provides a route to restore exactly the original picture when compression is reversed, different methods of lossy compression will restore an expanded picture with different kinds of information loss, and with different resulting artifacts that may compromise the visual quality. Massimo Ballerini’s Dark Method sacrifices the smaller numerical gradations in the color values at each pixel, while maintaining full spatial resolution in the picture after expansion. Although a similar result may be achieved by retaining fewer distinct color levels in the initial acquisition of the picture, the dark method begins with the conventional 256 or more levels for each color, and therefore provides the opportunity for nonlinear spacing of the reduced number of levels retained in the compression step, a way to provide higher picture quality at any selected amount of compression. Because the Dark Method does not directly exploit the eye’s limited ability to resolve fine spatial detail in chrominance, for example, I anticipate that the Dark Method would not normally be used alone, but would be combined with one or another of the more conventional means of lossy compression for a better joint result. Enhancement: Bidimensional Color Space, Tetrahedric Model, and Quadratic Color. These three technical proposals offer means of enhancing images, rather than compressing them. There advantage over previous art appears to be in providing easier and more efficient processes for enhancing the appearance of the images. In some cases a given kind of enhancement can be achieved with fewer individual manipulations than would be needed in the conventional use of image enhancement software. |