Multilevel image display method

A multilevel image display method for a multilevel image display apparatus, comprising:

• a grouping process for grouping together, as one data block, m pieces of digital data corresponding to m pixels, which are adjacent in a scanning direction, (m being an integer no less than two), the data block having phase 1, phase 2, . . . and phase m in the stated order in the scanning direction,
• an error calculation process for
• extracting the digital values separately for each phase of the data block;
• designating a target pixel for each phase of the data block, and
• calculating in parallel for each phase of the data block, a display error from a digital value that corresponds to a respective target pixel;
• an error diffusion process for diffusing each display error calculated in the error calculation process into digital values corresponding to pixels included in at least one data block that follows the data block including the target pixel;
• and
• a display process for converting the resulting digital values corresponding to each pixel in the data block into multilevel values that are used when displaying an image, and displaying an image based on the converted multilevel data.