Colour dithering using a space filling curve

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  • Technical report TR95-04. Recent results describe how a space-filling curve can be used as an error-diffusion path for half-toning of grey-scale images. The space-filling half-toning method produces clustered approximations to images with less regular artifacts than other available clustering methods. In this paper we present two methods for half-toning colour images using the space-filling technique. The first method processes the red, green, and blue (RGB) (or cyan, magenta, yellow, and black (CMYK)) channels independently, while the second method implements an interpolation between colours that lie on the corners of the RGB colour cube. The first method produces overlapping clusters of red, green, and blue pixels. This technique is useful when the display device allows the three colours to be set independently. For a variety of reasons it is often desirable to reduce the amount of ink used in the display of an image. The second method we present addresses this problem by approximating the regions of pixels with two sets of non overlapping colours. This results in image approximations with a guaranteed maximum pixel coverage of one or two inks (100% or 200% coverage). The quality of image reproduction is severely compromized when this approach is used. Nevertheless, the technique does provide a guarantee of maximum coverage. These results allow the use of the space-filling technique for dithering colour images. We illustrate the performance of these methods using two images that are printed in various ways on a 300 DPI ink-jet printer. The results are primarily geared to printers, since most modern computer displays allow the selection of specialized palettes, thus making quantization results applicable. | TRID-ID TR95-04

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    Attribution 3.0 International