Method and apparatus for image processing, and a computer product

An image processing apparatus which varies resolution of an image and a gradation level of the pixels composing the image, the image processing apparatus comprising:

• a gradation direction determining means for determining a gradation direction which is a direction of a contrast of the gradation at the pixel position of a target pixel;
• a spatial frequency determining means for determining a spatial frequency at the pixel position of the target pixel;
• a dividing means for dividing the target pixel into fine pixels;
• and
• a gradation determining means for determining a gradation level of the fine pixel produced by the dividing means based on the gradation level of the target pixel, the gradation direction determined by the gradation direction determining means and the spatial frequency determined by the spatial frequency determining means.

An image processing method of varying resolution of an image and gradation level of the pixels composing the image, the image processing method comprising the steps of:

• determining a gradation direction which is a direction of a contrast of the gradation at the pixel position of a target pixel;
• determining a spatial frequency at the pixel position of the target pixel;
• dividing the target pixel into fine pixels;
• and
• determining a gradation level of the fine pixel produced in the dividing step based on the gradation level of the target pixel, the gradation direction determined in the gradation direction determining step and the spatial frequency determined in the spatial frequency determining step.

A computer readable medium for storing instructions, which when executed by a computer, causes the computer to perform the steps of:

• determining a gradation direction which is a direction of a contrast of the gradation at the pixel position of a target pixel;
• determining a spatial frequency at the pixel position of the target pixel;
• dividing the target pixel into fine pixels;
• and
• determining a gradation level of the fine pixel produced in the dividing step based on the gradation level of the target pixel, the gradation direction determined in the gradation direction determining step and the spatial frequency determined in the spatial frequency determining step.