Patent ID: 8331705

Claim:
An image encoding apparatus for encoding image data, comprising: an input unit which inputs a block of 2×2 pixels from original image data of an encoding target; a reduced image generator which generates and outputs reduced image data having a size smaller than the original image data by sampling one pixel data at a preset position in the input block; and an encoder which generates encoded data to restore three non-sampling target pixel data in each block so as to restore the original image data from the reduced image data generated by said reduced image generator, wherein said encoder comprising: a determination unit which, letting X be a sampling target pixel in a block of interest, and Xa, Xb, and Xc be non-sampling target pixels in the block of interest, determines condition (a): whether all the pixels Xa, Xb, and Xc are restorable from the pixel X in the block of interest, and condition (b): whether all the pixels Xa, Xb, and Xc are restorable from sampling target pixels in three blocks adjacent to the block of interest; and an additional information generator which generates first additional information as encoded data of the block of interest when said determination unit has determined that the block of interest satisfies the condition (a), generates second additional information different from the first additional information as the encoded data of the block of interest when said determination unit has determined that the block of interest satisfies not the condition (a) but the condition (b), and generates third additional information different from the first additional information and the second additional information as the encoded data of the block of interest when said determination unit has determined that the block of interest satisfies neither the condition (a) nor the condition (b).