Patent ID: 8111429

Claim:
A dithering apparatus for expressing a high-tone input image of M+K bits, where M and K are integers >1, on a low-tone output device of M bits, the apparatus comprising: a mask-pattern-generating unit that generates one mask pattern for an R channel, a G channel or a B channel by selecting pattern values constituting the mask pattern based on randomly-determined seed values, and generates two other mask patterns, one by inverting pattern values of the generated mask pattern and another by rotating pattern values of the generated mask pattern; a spatial-weight-determining unit that determines a spatial weight for spatial dithering by using the pattern values and K-bit least significant bit (LSB) data of the high-tone input image; and an output unit that outputs an M-bit image by applying the spatial weight to M-bit input image data, exempting the K-bit LSB data, in a dithering apparatus for expressing the M+K bit high-tone input image in the M-bit low-tone output device.