Image preprocessing
AssigneeApple Inc.
InventorRobert Mikio Free
Life of this patent
Estimating the term…
Abstract
A method performed by a software process executing on a computer system, includes obtaining a digital image having a plurality of pixels encoded in a YUV color space. Each pixel has a luma component of value Y, a blue color-difference component of value U and a red color-difference component of value V. For a specified pixel, the method includes calculating whether U is less than a first threshold and V is greater than a second threshold. The method further includes determining whether the specified pixel potentially depicts an orange hue depending on a result of the calculation.
Claims19
A method performed by a software process executing on a computer system, the method comprising:
- obtaining a digital image comprising a plurality of pixels encoded in a YUV color space, each pixel having a luma component of value Y, a blue color-difference component of value U and a red color-difference component of value V;
- for a specified pixel having values of the blue color-difference and red color-difference components that correspond to a point (U, V) in a U-V color plane of the YUV color space, calculating whether U is less than a first threshold and V is greater than a second threshold;
- determining whether the specified pixel potentially depicts an orange hue depending on a result of the calculation, and
- calculating a chroma value for the specified pixel by determining a distance of the point (U,V) from the origin on the U-V color plane, wherein the distance of the point (U,V) from the origin on the U-V color plane is calculated as an average of U and V.
A system comprising:
- one or more hardware processors;
- a non-transitory storage medium storing instructions that when executed by the one or more hardware processors cause the system to perform operations comprising:
- selecting a first set of pixels in a digital image in the YUV color space such that, for each pixel in the set, a U component is less than a first threshold and a V component is greater than a second threshold;
- identifying at least a subset of the first set as a region of orange hue in the digital image, and
- calculating a chroma value for a specified pixel with components that correspond to a point (U, V) in a U-V color plane of the YUV color space, at least in part, by determining a distance of the point (U,V) from the origin on the U-V color plane, wherein the distance of the point (U,V) from the origin on the U-V color plane is calculated as an average of U and V.
A non-transitory computer-readable medium encoding instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising:
- accessing a digital image comprising a plurality of pixels encoded in a color space that defines hue as a pair of Cartesian coordinates;
- calculating a chroma value for a specified pixel by determining a distance between a point corresponding to a hue coordinate pair value for the specified pixel in the digital image and a Cartesian origin point;
- comparing the calculated chroma value to a predetermined threshold;
- and
- performing an image processing operation on the digital image based on a result of the comparison,
- wherein performing the image processing operation includes using hue information if the calculated chroma value meets or exceeds the predetermined threshold and using luminosity information if the calculated chroma value is less than the predetermined threshold.
Dependencies are inferred from the claim text.