| 摘要 |
<p>PROBLEM TO BE SOLVED: To allow an image coder to efficiently compress an image by automatically discriminating an image whose density is fluctuated in addition to a photographing image and a character image without the need for selecting a compression method. SOLUTION: A frequency conversion section 102 converts image data consisting of n×m pixels into a frequency conversion coefficient and a density conversion section 103 converts the image data consisting of n×m pixels into a density conversion coefficient. An area discrimination section 104 and a selection section 105 discriminate whether or not number of different densities in a block consisting of n×m pixels is a prescribed value and whether or not a difference between pixel values in virtual blocks whose number of different densities is within a prescribed range, select the frequency conversion coefficient for blocks where the conditions above are not satisfied and select the density conversion coefficient for blocks where either of the conditions is satisfied.</p> |
