Patent ID: 7773820
Filing Date: 2010-08-10
Classification: H04N

Abstract:
1. A data compression apparatus that applies a data compression processing to data to be compressed, in which a two-dimensional image is represented by a succession of numerical values represented by a predetermined number of unit bits, the data compression apparatus comprising: a thinning processing means for periodically thinning numerical values from the succession of numerical values constituting compressed data so as to create a first compressed data consisting of a succession of numerical values derived from thinned compressed data, and a second compressed data consisting of a succession of remained numerical values; a reversible compression means for applying reversible compression processing to the first compressed data created by the thinning processing means; a detecting means for detecting an edge portion of the image; and a non-reversible compression means for providing such processing that (1) when the detecting means detects no edge portion on the numerical values constituting the second compressed data created in the thinning processing means, the non-reversible compression means outputs a predetermined code of a number of bits that is less than the predetermined number of unit bits, (2) when the detecting means detects the edge portion on the numerical values constituting the second compressed data created by the thinning processing means, the non-reversible compression means outputs (2a) a numerical value that is obtained by expressing one of the numerical values constituting the second compressed data by a first number of bits that is less than the predetermined number of unit bits if the one of the numerical values constituting the second compressed data is involved in a predetermined positional relation on the image with the numerical values constituting the first compressed data, and (2b) a numerical value that is obtained by expressing one of the numerical values constituting the second compressed data by a second number of bits that is less than the first number of bits if the one of the numerical values constituting the second compressed data is not involved in the predetermined positional relation on the image with the numerical values constituting the first compressed data.