System and method for eliminating background pixels from a scanned image

An image processing system for reproducing an image formed of a plurality of pixels each represented by an image grey value and for suppressing background grey values of the image, the system comprising:

• a grey value histogram generator for generating histogram data representing frequencies of the image grey values;
• a background determiner for determining a peak grey value from the histogram data, the peak grey value being set as a background threshold value defining background grey values to be suppressed;
• and
• a thresholding circuit for dynamically adjusting the background threshold value to increase a number of the background grey values to be suppressed, the thresholding circuit adjusting the background threshold value based on a standard deviation from the peak grey value.

A method suppressing a background mage from a document being reproduced, the document being formed of a plurality of video pixels each having a grey alue, the method comprising the steps of:

• generating a arey value histogram representing a frequency of occurrence of the grey values based on the plurality of video pixels;
• determining a background peak grey value from the histogram, the background peak grey value being a grey value having a greatest frequency of occurrence in the histogram, the background peak grey value being a basis for identifying a range of grey values representing the background image;
• expanding the range of grey values representing the background image by scaling the background peak grey value;
• and
• reproducing the document without the range of grey values representing the background image.

An image processing system for reproducing an image formed of a plurality of pixels each represented by an image grey value and for suppressing background grey values of the image, the system comprising:

• a histogram generator for generating histogram data representing frequencies of the image grey values;
• a background determiner for determining a peak grey value from the histogram data, the peak grey value being set as a background threshold value defining the background grey values to be suppressed;
• and
• a thresholding circuit for dynamically adjusting the background threshold value to increase a number of the background grey values to be suppressed, the thresholding circuit adjusting the background threshold value based on an equation:
• background threshold value=peak grey value−scaling factor*(2 sigma), where the scaling factor is selectable by a user, between 0 and 2⅞ in ⅛ increments, and 2 sigma is about 2 standard deviations from the peak grey value based on the histogram data.