Image decoding apparatus using pixel values from at least three reference pixels

An image coding apparatus for successively coding, block by block, each block comprising a prescribed number of pixels, pixel values constituting an image signal on the basis of pixel values of plural peripheral pixels positioned in the vicinity of a coding target pixel, comprising:

• blocking means for blocking an image signal comprising plural pixels into blocks, each block having a square form and comprising N×N pixels;
• pixel value replacing means for replacing a pixel value of an uncoded pixel among plural peripheral pixels positioned in the vicinity of a coding target pixel, the peripheral pixels including at least three lines of pixels and the target pixel being in the third line, with a pseudo pixel value obtained from a pixel value of a coded pixel among the plural peripheral pixels;
• wherein the pixel value replacing means employs, as the pseudo pixel value of the uncoded pixel, a pixel value of a coded pixel that is positioned at the shortest distance from the uncoded pixel and on the same horizontal scanning line among said three lines of pixels;
• coding means for (a) performing, block by block, a coding process in which the respective pixels of a coding target block are coded using pixel values of at least one coded pixel positioned in each of a previously coded block and the coding target block, and a pseudo pixel value of an uncoded pixel, and wherein the respective pixels are coded on the basis of
• i) the pixel value of a coded pixel positioned in a previously coded block for the peripheral pixel positioned in a previously coded block;
• ii) the pixel value of a coded pixel positioned in the coding target block for the peripheral pixel positioned in the coding target block;
• and
• iii) a pseudo pixel value of the uncoded pixel for the peripheral pixels positioned in an uncoded block,
• and (b) outputting a coded image signal corresponding to each block.