Document registration and skew detection system

A method, comprising:

• generating a digital representation of a scan image that represents an input document positioned in a scan area;
• identifying pixels of said scan image that correspond to a first captured portion of said input document;
• detecting scan image scanlines that correspond to a plurality of input document edges;
• and
• generating registration information for said input document reproduction based upon at least one of said input document skew angle and said input document shear amount.

A method, comprising:

• receiving a scan image that digitally represents an input document positioned in a scan area;
• and
• detecting a fast-scan direction aligned input document edge by (i) obtaining a first grayscale average for a scan image target pixel and a pixel aligned with said target pixel in a slow-scan direction in a first previously processed scanline, (ii) obtaining a second grayscale average for pixels that are aligned with said target pixel in a slow-scan direction in at least a second and third previously processed scanline, (iii) obtaining a difference between said first grayscale average and said second grayscale average;
• (iv) obtaining a grayscale difference threshold that distinguishes background pixels and input document pixels and (v) designating said target pixel as a slow-scan transition pixel if said first and second grayscale average difference exceeds said grayscale difference threshold.