Neutral pixel detection using color space feature vectors wherein one color space coordinate represents lightness

A method for neutral pixel detection for use in color image processing, comprising the following steps:

• a) receiving an input image represented in a first color space;
• b) converting the input image to a second color space wherein one coordinate of the second color space represents lightness, the second color space being an L*a*b* color space;
• c) selecting a pixel in the second color space representation of the input image;
• d) computing second color space feature vectors associated with the selected pixel including,
• d1) selecting a pixel window associated with the selected pixel,
• d2) computing a first feature vector (V1) based on the selected pixel, computed using the eguation:
• V1=L*(x,y)/255,
• wherein (x,y) are coordinates for the selected pixel within the selected pixel window,
• d3) computing a second feature vector (V2) based on the selected pixel window, and
• d4) computing a third feature vector (V3) based on the selected pixel window;
• and
• e) detecting if the selected pixel is neutral based on the values computed for the second color space feature vectors.

A method for classifying pixels of an input image between neutral and color classes for use in color image processing, comprising the following steps:

• a) receiving a first strip of an input image represented in a first color space wherein the strip is comprised of a plurality of scanlines;
• b) converting the input image strip to a second color space wherein one coordinate of the second color space represents lightness;
• c) selecting a first pixel in the second color space representation of the input image strip to be classified;
• d) computing second color space feature vectors associated with the selected pixel;
• e) classifying the selected pixel between neutral and color classes based on the values computed for the second color space feature vectors;
• f) determining if any additional pixels of the input image strip to be classified have not been classified;
• g) if any additional pixels to be classified have not been classified, selecting a next pixel in the second color space representation of the input image strip to be classified and repeating steps d) through f);
• h) determining if any additional scanlines in the input image have not been received in an input image strip;
• and
• i) if any additional scanlines have not been received in an input image strip, appending one or more next scanlines in the input image to the strip while ousting one or more corresponding scanlines from the strip in a first-in-first-out fashion and repeating steps b) through g).