Image processing apparatus and image processing method

A computer readable non-transitory storage medium having stored therein an image processing program for generating a smoothed image obtained by blurring an input image, the image processing program causing a computer to execute a process comprising:

• setting pixels of the input image as process target pixels by using a plurality of first low pass filters each having a plurality of different level value ranges;
• computing average values of the pixels included in the level value ranges from the pixels of the input image including process target pixels included within the filter sizes of the plurality of first low pass filters;
• generating a plurality of level-value-limited smoothed images limited by the plurality of level values;
• setting the pixels of the input image as process target pixels by using a plurality of second low pass filters each having a plurality of level value ranges or filter sizes different from those of the first low pass filters;
• computing average values of the pixels included in the level value ranges from the pixels of the input image including process target pixels included within the filter sizes of the second low pass filters;
• generating a plurality of level-value-limited smoothed images limited by the plurality of level values;
• selecting one or more of the level-value-limited smoothed images generated for the first or the second low pass filters on the basis of the process target pixels and level values different from the level values utilized for the first and second low pass filters;
• and
• generating a smoothed image that uses values computed from level values of one or more of the pixels located at a position of the process target pixel or positions near the process target pixel in the selected one or more of the level-value-limited smoothed images as the level values of the process target pixels.

An image processing method of generating a smoothed image obtained by blurring an input image, the image processing method comprising:

• setting pixels of the input image as process target pixels by using a plurality of first low pass filters each having a plurality of different level value ranges;
• computing average values of the pixels included in the level value ranges from the pixels of the input image including process target pixels included within the filter sizes of the plurality of first low pass filters;
• generating a plurality of level-value-limited smoothed images limited by the plurality of level values;
• setting the pixels of the input image as process target pixels by using a plurality of second low pass filters each having a plurality of level value ranges or filter sizes different from those of the first low pass filters;
• computing average values of the pixels included in the level value ranges from the pixels of the input image including process target pixels included within the filter sizes of the second low pass filters;
• generating a plurality of level-value-limited smoothed images limited by the plurality of level values;
• selecting one or more of the level-value-limited smoothed images generated for the first or the second low pass filters on the basis of the process target pixels and level values different from the level values utilized for the first and second low pass filters;
• and
• generating a smoothed image that uses values computed from level values of one or more of the pixels located at a position of the process target pixel or positions near the process target pixel in the selected one or more of the level-value-limited smoothed images as the level values of the process target pixels.