Image decoding apparatus, image decoding method, image coding apparatus, and image coding method
AssigneeSharp Kabushiki Kaisha
InventorsYukinobu Yasugi, Tomoyuki Yamamoto, Tomohiro Ikai, Takeshi Tsukuba
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Abstract
In a case that a pixel shape in a luma domain is not similar to a pixel shape in a chroma domain in an input image, a prediction image that is generated in the reuse of a luma prediction mode is made more accurate. A moving image decoding apparatus 1 includes a gradient deriving unit 1453B that references a chroma gradient definition DEFANG1C, and derives a chroma prediction direction from a prediction mode based on a luma prediction direction.
Claims8
An image decoding apparatus for decoding an image by generating prediction images using by an intra prediction mode, the image decoding apparatus comprising:
- a circuit;
- wherein
- the circuit is configured to derive a chroma prediction mode based on a luma prediction mode;
- and
- the circuit is configured to generate a chroma prediction image by the chroma prediction mode,
- wherein the circuit is configured to derive, in a case that a chroma prediction mode index included in coded data is one:
- (i) the chroma prediction mode as an angular prediction mode in a case that the luma prediction mode is a vertical mode, and
- (ii) the chroma prediction mode as a vertical prediction mode in a case that the luma prediction mode is a planar prediction mode.
An image decoding method for decoding an image by generating prediction images using by an intra prediction mode, the image decoding method comprising the steps of:
- (a) deriving a chroma prediction mode based on a luma prediction mode;
- and
- (b) generating a chroma prediction image by the chroma prediction mode,
- in the step (a), in a case that a chroma prediction mode index included in coded data is one:
- (i) deriving the chroma prediction mode as an angular prediction mode in a case that the luma prediction mode is a vertical mode, and
- (ii) deriving the chroma prediction mode as a vertical prediction mode in a case that the luma prediction mode is a planar prediction mode.
An image coding apparatus for coding an image by generating prediction images using by an intra prediction mode, the image coding apparatus comprising:
- a circuit;
- wherein
- the circuit is configured to derive a chroma prediction mode based on a luma prediction mode;
- and
- the circuit is configured to generate a chroma prediction image by the chroma prediction mode,
- wherein the circuit is configured to derive, in a case that a chroma prediction mode index is one:
- (i) the chroma prediction mode as an angular prediction mode in a case that the luma prediction mode is a vertical mode, and
- (ii) the chroma prediction mode as a vertical prediction mode in a case that the luma prediction mode is a planar prediction mode.
An image coding method for coding an image by generating prediction images using by an intra prediction mode, the image coding method comprising the steps of:
- (a) deriving a chroma prediction mode based on a luma prediction mode;
- and
- (b) generating a chroma prediction image by the chroma prediction mode, in the step (a), in a case that a chroma prediction mode index is one:
- (i) deriving the chroma prediction mode as an angular prediction mode in a case that the luma prediction mode is a vertical mode, and
- (ii) deriving the chroma prediction mode as a vertical prediction mode in a case that the luma prediction mode is a planar prediction mode.
Dependencies are inferred from the claim text.