| 摘要 |
Image data is divided into blocks, each block has M×N pixels, the number of colors of each block undergoes reduction from M×N to each number of one to (M×N−1). Differences between pixel values for each block after color reduction, and pixel values for each block before first color reduction. A first table in which thresholds are associated with either the amount of data to be reduced or the amount of data to be remained, is acquired based on the acquired difference. A threshold at which the amount of data after compression drops to or below a target data amount is specified, based on the first table, and compressed data is generated based on image data after second color reduction using the specified threshold. |
