Patent ID: 8254703
Filing Date: 2012-08-28
Classification: H04N

Abstract:
1. An image compression apparatus comprising: a dividing section for dividing an image to be compressed into blocks, each of which has a predetermined number of pixels having respective gradation value; a maximum value and minimum value search section for obtaining a maximum value and a minimum value of gradation values of the predetermined number of pixels in each block obtained by the dividing section; a discrimination section for determining whether each block of the divided blocks is a first kind block, in which an outline portion of the image is not included and a difference between the maximum value and the minimum value of the block is equal to or greater than a reference value or a second kind block other than the first kind block; and a normalization output section which divides a distribution range of gradation values, both ends of which correspond to the maximum value and the minimum value of each block of the divided blocks, in a case where a discrimination result of the discrimination section with respect to the block is the second kind block, into N areas (where N is an integer which is equal to 2 or greater) and outputs compressed data containing code data for showing to which area in the N areas, each pixel in each block belongs, and the maximum value and the minimum value, and which divides a distribution range of gradation values, both ends of which correspond to the maximum value and the minimum value of each block of the divided blocks, in a case where a discrimination result of the discrimination section with respect to the block is the first kind block, into M areas (where M is an integer which is greater than N) and outputs compressed data containing code data for showing to which area in the M areas, each pixel in each block belongs, the maximum value and the minimum value; wherein in a case of the first kind block, the normalization output section arranges the maximum value and the minimum value related to the block in a first order in a head portion of the compressed data, and in a case of the second kind block, the normalization output section arranges the maximum value and the minimum value related to the block in a second order that is a reverse order of the first order in a head portion of the compressed data.