Sun Microsystems, Inc.

Grant J Williamson

Stuart C Wells

The method and apparatus of the present invention takes into consideration that the eye is more sensitive to intensity variations at low levels of intensity than at high levels of intensity and produces higher quality dithered images by employing a sectioned or piecewise linear quantization strategy which sacrifices the fineness of interval spacing at the high end of the intensity scale in order to achieve greater accuracy of reproduction at the low end. The input intensity values are divided into a plurality of sub-ranges indicative of low intensities and high intensities. The number of input intensity levels allocated to the low intensity sub-ranges is small and the number of quantized or output intensity levels allocated to the low intensity sub-ranges is large compared to those allocated to the high intensity sub-ranges such that the interval spacing at the low intensity sub-ranges is small to provide greater accuracy at the low intensity levels where the eye is most sensitive.

Method and apparatus for non-linear dithering of digital images

A method and apparatus for dithering vectors in which the dither matrix is aligned to the vector and not to the display coordinate space. The dither matrix is aligned to the vector according to the major axis of the vector. In a preferred embodiment the dither matrix is rectangular in shape to correspond to the shape of the vector. The vector aligned dither matrix ensures that the individual pixels which make up the vector are dithered with elements more likely to simulate the original intermediate intensities.

Method and apparatus for vector aligned dithering

In the method and apparatus of the present invention, dithered images are composited with separately rendered undithered images. The dithered image is first transformed back to its unquantized state to include the full range of intensity values by performing a back-transforming process which translates the quantized or dithered value back to its original intensity value. The back transformed dithered image is then combined with the separately rendered, but undithered image using the technique of compositing. The composited image is then dithered to a quantized representation are stored in the frame buffer for subsequent display.

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Sunnyvale, CA, United States of America

Grant J Williamson