Dithering for Chromatically Subsampled Image Formats
AssigneeDolby Laboratories Licensing Corporation
InventorsScott DALY, Bongsun LEE
Life of this patent
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Abstract
Dithering techniques for images are described herein. An input image of a first bit depth is separated into a luma and one or more chroma components. A model of the optical transfer function (OTF) of the human visual system (HVS) is used to generate dither noise which is added to the chroma components of the input image. The model of the OTF is adapted in response to viewing distances determined based on the spatial resolution of the chroma components. An image based on the original input luma component and the noise-modified chroma components is quantized to a second bit depth, which is lower than the first bit depth, to generate an output dithered image.
Claims24
A method to dither images using a processor, the method comprising:
- receiving an input image in a first bit depth, the input image represented in a first color format comprising a luma component and one or more chroma components;
- generating white noise;
- filtering the white noise according to the inverse of an optical transfer function (OTF) of the human visual system (HVS) to generate dither noise, wherein the OTF is adapted in response to at least a horizontal viewing distance or a vertical viewing distance;
- and
- adding the dither noise to the one or more chroma components to generate noise-modified chroma components.
A method to dither images using a processor, the method comprising:
- receiving an input image in a first bit depth, the input image represented in a first color format comprising a luma component in a first spatial resolution and one or more chroma components in a second spatial resolution, the second spatial resolution being lower than the first spatial resolution in at least a vertical or a horizontal direction;
- generating white noise;
- filtering the white noise according to the inverse response of a first low-pass filter to generate chroma dither noise, wherein the response of the first low-pass filter is adapted in response to the second spatial resolution;
- filtering the white noise according to the inverse response of a second low-pass filter to generate luma dither noise, wherein the response of the second low-pass filter is adapted in response to the first spatial resolution;
- adding the luma dither noise to the luma component to generate a noise-modified luma component;
- adding the chroma dither noise to the one or more chroma components to generate noise-modified chroma components;
- and
- generating an output dithered image in a second bit depth in response to quantizing the noise-modified luma component and the noise-modified chroma components, wherein the second bit depth is lower than the first bit depth.
Dependencies are inferred from the claim text.