A density detector detects a first density of a first pattern and a second density of a second pattern from a density-correction determination patch. A density-correction-value calculator calculates a density correction value from the first and the second densities. A noise-occurrence determination unit determines whether a target pixel is a noise generating pixel that causes a change of a local density due to a change in a relation with a nearby pixel. A density correction processor performs a density correction process on the target pixel by adding or subtracting the density correction value to or from the target pixel or the nearby pixel.