Image data encoding/decoding method and apparatus

Abstract

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; combining the generated prediction image with 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. The step of generating the prediction image includes the steps of: performing image extension of a reference picture obtained by reconstructing the bitstream; and generating a prediction image by making reference to the reference picture extended by the image extension.

What is claimed is: 
     
         1 . A method of decoding a 360-degree image, the method comprising:
 receiving a bitstream obtained by encoding the 360-degree image;   generating a predicted image with reference to syntax information acquired from the received bitstream;   acquiring a decoded image by combining the generated predicted image with a residual image acquired by inversely quantizing and inversely transforming the bitstream; and   reconstructing the decoded image to produce a 360-degree image corresponding to a projection format,   wherein the generating of the predicted image comprises:
 performing image expansion on a reference image acquired by restoring the bitstream; and 
 generating a predicted image with reference to the reference image on which the image expansion is performed. 
   
     
     
         2 . The method of  claim 1 , wherein the performing of the image expansion comprises performing the image expansion on the basis of segmentation units of the reference image. 
     
     
         3 . The method of  claim 2 , wherein the performing of the image expansion on the basis of the segmentation units comprises generating a region expanded individually for each of the segmentation units, using boundary pixels of the segmentation units. 
     
     
         4 . The method of  claim 3 , wherein the expanded region is generated using a boundary pixel of a segmentation unit spatially adjacent to a segmentation unit to be expanded or using a boundary pixel of a segmentation unit having image continuity with a segmentation unit to be expanded. 
     
     
         5 . The method of  claim 2 , wherein the performing of the image expansion on the basis of the segmentation units comprises generating an expanded image for a region where two or more segmentation units that are spatially adjacent to each other among the segmentation units are combined, using a boundary pixel of the combined region. 
     
     
         6 . The method of  claim 2 , wherein the performing of the image expansion on the basis of the segmentation units comprises generating a region expanded between segmentation units that are spatially adjacent to each other among the segmentation units, using all adjacent pixel information of the adjacent segmentation units. 
     
     
         7 . The method of  claim 6 , wherein the performing of the image expansion on the basis of the segmentation units comprises generating the expanded region using an average value of adjacent pixels of each of the spatially adjacent segmentation units.