Apparatus for detecting text edges in digital image processing

Apparatus for detecting edges of text in an original image, said apparatus comprising:

• A. input means for providing a digital signal representative of an original image;
• B. an edge detector having:
• a) edge blurring means for sequentially low pass filtering a provided digital signal to blur and widen any edges in the original image,
• b) means for high pass filtering the low pass filtered signal to produce a first output signal which represents the edges of the blurred original image,
• c) non-edge blurring means for high pass filtering the provided signal to produce a second output signal which represents the non-blurred edges in the original image, and
• d) means for combining the first and second output signals to create a first edge control signal that encompasses any edges in the original image;
• C. a half tone area detector having:
• a) means for identifying halftone areas of the original image by identifying those areas of the original image that contain dots, and
• b) means for creating a second edge control signal that excludes areas in the original image identified as containing dots;
• and
• D. means for combining said first and second edge control signal to create a text edge control signal that encompasses edges in the original image not in an area that contains dots.

A black edge detector for digital color image processing apparatus, said edge detector comprising:

• input means for providing a digital signal representative of an original image;
• edge blurring means for sequentially low pass filtering the provided signal to blur and widen any edges in the original image;
• means for high pass filtering the low pass filtered signal to produce a first output signal which represents the edges of the blurred original image;
• non-edge blurring means for high pass filtering the inputted signal to produce a second output signal which represents the non-blurred edges in the original image;
• means for combining the first and second output signals to create a text edge control signal that encompasses any edges in the image represented by the provided digital signal;
• means for discriminating between color pixels and neutral pixels in the provided signal to produce a neutral color signal that represents the non-color portions of the original image;
• and
• means for combining the text edge control signal and the neutral color signal to create a black text edge control signal.

Apparatus for detecting edges of black text in an original image, said apparatus comprising:

• A. input means for providing a digital signal representative of an original image;
• B. an edge detector having:
• a) edge blurring means for sequentially low pass filtering a provided digital signal to blur and widen any edges in the original image,
• b) means for high pass filtering the low pass filtered signal to produce a first output signal which represents the edges of the blurred original image,
• c) non-edge blurring means for high pass filtering the provided signal to produce a second output signal which represents the non-blurred edges in the original image, and
• d) means for combining the first and second output signals to create a first edge control signal that encompasses any edges in the original image;
• C. a halftone area detector having:
• a) means for identifying halftone areas of the original image by identifying those areas of the original image that contain dots, and
• b) means for creating a second edge control signal that excludes areas in the original image identified as containing dots;
• D. means for discriminating between color pixels and neutral pixels in the provided signal to produce a neutral color signal that represents the non-color portions of the original image;
• and
• E. means for combining said first edge control signal, said second edge control signal, and said neutral color signal to create a black text edge control signal that encompasses edges in the original image not in an area that contains dots.