Method for detecting an image edge within a dithered image

A method for detecting an image edge within a dithered image, the method comprising the steps of:

• selecting for processing a pixel within a support region of the dithered image, the support region encompassing a plurality of pixels each having a pixel value, the pixel value being one of a plurality of resolution levels;
• computing a table of difference maps for the region, the difference maps within the table describing a constant color or gray scale region;
• forming a current difference map by computing a difference between the value of each pixel in the region and the value of the selected pixel;
• comparing the current difference map to the difference maps within the table;
• and
• determining that an image edge exists within the region, if there is no difference map within the table that matches the current difference map.

A computer readable medium having computer-readable instructions for performing a method for detecting an image edge within a dithered image, the method comprising:

• selecting for processing a pixel within a support region of the dithered image, the support region encompassing a plurality of pixels each having a pixel value, the pixel value being one of a plurality of resolution levels;
• forming a current difference map by computing a difference between the value of each pixel in the region and the value of the selected pixel;
• and
• determining from the current difference map that an image edge exists within the region if any pixel values in the region differ from each other by more than one resolution level.

A computer readable medium having computer-readable instructions for performing a method for detecting an image edge within a dithered image, the method comprising:

• selecting for processing a pixel within a support region of the dithered image, the support region encompassing a plurality of pixels each having a pixel value, the pixel value being one of a plurality of resolution levels;
• computing a table of difference maps for the region, the difference maps within the table describing a constant color or gray scale region;
• forming a current difference map by computing a difference between the value of each pixel in the region and the value of the selected pixel;
• comparing the current difference map to the difference maps within the table;
• and
• determining that an image edge exists within the region, if there is no difference map within the table that matches the current difference map.