Method and apparatus for reconstructing 360-degree image according to projection format
Disclosed are methods and apparatuses for image data encoding/decoding. A method for decoding a 360-degree image includes the steps of: receiving a bitstream obtained by encoding a 360-degree image; generating a prediction image by making reference to syntax information obtained from the received bitstream; adding the generated prediction image to a residual image obtained by dequantizing and inverse-transforming the bitstream, so as to obtain a decoded image; and reconstructing the decoded image into a 360-degree image according to a projection format. Therefore, the performance of image data compression can be improved.
1. A method of decoding an image, comprising:
obtaining at least one offset for a picture;
deriving a variable for scaling for the picture based on the at least one offset; and
performing inter prediction based on the variable for scaling for the picture,
wherein the at least one offset is defined with a direction of scaling,
wherein the at least one offset is a plus value or a minus value,
wherein the at least one offset comprises a left offset and a right offset,
wherein the at least one offset is signaled for a chroma component, and
wherein the variable for scaling for a luma component is derived by multiplying the at least one offset by 2 in case a ratio of the luma component to the chroma component is 2 to 1.
2. The method of claim 1 , wherein the at least one offset further comprises a top offset and a bottom offset.
3. The method of claim 2 , wherein the variable for scaling in a vertical direction is derived based on the top offset and the bottom offset.
4. A method of encoding an image, comprising:
determining at least one offset for a picture;
deriving a variable for scaling for the picture based on the at least one offset; and
performing inter prediction based on the variable for scaling for the picture,
wherein the at least one offset is defined with a direction of scaling,
wherein the at least one offset is a plus value or a minus value,
wherein the at least one offset comprises a left offset and a right offset,
wherein the at least one offset is signaled for a chroma component, and
wherein the variable for scaling for a luma component is derived by multiplying the at least one offset by 2 in case a ratio of the luma component to the chroma component is 2 to 1.
5. A method of transmitting a bitstream that is generated by an image encoding method, the image encoding method comprising:
determining at least one offset for a picture;
deriving a variable for scaling for the picture based on the at least one offset;
performing inter prediction based on the variable for scaling for the picture; and
transmitting the bitstream including the at least one offset,
wherein the at least one offset is defined with a direction of scaling,
wherein the at least one offset is a plus value or a minus value,
wherein the at least one offset comprises a left offset and a right offset,
wherein the at least one offset is signaled for a chroma component, and
wherein the variable for scaling for a luma component is derived by multiplying the at least one offset by 2 in case a ratio of the luma component to the chroma component is 2 to 1.