Method and apparatus for image enhancement using intensity dependent spread filtering

An apparatus for recognizing a character in an image in the form of pixel data, comprising:

• input means for inputting image data into the apparatus;
• means for smoothing and thinning the input image data;
• means for segmenting adjacent characters in the smoothed and thinned data;
• and
• a character recognizer for identifying a segmented character based on a comparison of the segmented character to smooth a dictionary of characters, wherein said means for smoothing and thinning comprises:
• means for applying to each pixel a filter whose spread depends on variations in image intensity in surrounding pixels to convert inputted image data into filtered image data;
• means for obtaining differential data of the filtered image data;
• means for deriving inverted image data from the differential data of the filtered image data;
• and
• a multiplier for multiplying the inverted image data and the filtered image data to obtain smoothed and thinned image data.

Apparatus for recognizing a character in a pixel image original, comprising:

• input means for inputting the pixel image in the apparatus;
• means for deriving for each pixel of the pixel image a filter that depends on variations in intensity of surrounding pixels;
• means for applying each said filter to the pixel image to obtain a filtered image;
• means for obtaining differential data of the filtered image;
• means for deriving an inverted image from the differential data of the filtered image;
• means for multiplying the inverted image and the filtered image to obtain a smoothed and thinned image;
• a character segmenter for segmenting characters in the smoothed and thinned image;
• a character recognizer for comparing each segmented character to a character dictionary to identify characters;
• and
• a memory for storing the identity of the identified characters.

Apparatus for recognizing a character in a pixel image, comprising:

• input means for inputting the pixel image to the apparatus;
• a first memory for storing process steps that (a) derive for each pixel of the pixel image a filter that depends on variations in intensity of surrounding pixels, (b) apply each said filter to the pixel image, (c) obtain differential data of the filtered image, (d) derive an inverted image from the differential data of the filtered image, and (e) multiply the inverted image and the filtered image so as to obtain a smoothed and thinned image;
• a processor cooperating with said first memory to execute the process steps stored in said first memory so as to form a smoothed and thinned image from the pixel image;
• a second memory for storing the smoothed and thinned image formed by said processor;
• and
• means for determining the character represented by the smoothed and thinned image stored in said second memory.