Image recognition method and apparatus utilizing edge detection based on magnitudes of color vectors expressing color attributes of respective pixels of color image
First Claim
1. An image recognition method of processing image data of a color image which is represented as respective sets of color attribute data of an array of pixels, to successively operate on each of said pixels as an object pixel for thereby determining whether said object pixel is located on an edge within said color image, and thereby derive shape data expressing an edge image corresponding to said color image, the method comprising steps of:
- expressing said sets of color attribute data of each of said pixels as respective color vectors, with each said color vector defined by a plurality of scalar values which are coordinates of an orthogonal color space;
for each of a plurality of predetermined edge directions, generating a corresponding edge template as an array of respectively predetermined numeric values;
extracting an array of color vectors a respective color vectors of an array of said pixels, said array of pixels being centered on said object pixel;
successively applying each of said edge templates to said array of color vectors in a predetermined array processing operation, to derive edge vectors respectively corresponding to said edge directions;
comparing the respective moduli of said derived edge vectors to obtain a value of edge strength for said object pixel, as a maximum value of modulus of said edge vectors, and obtaining a possible edge direction for said object pixel as a direction corresponding to an edge vector having said maximum value of modulus; and
judging whether said object pixel is located on an actual edge which is oriented in said possible edge direction, based upon comparing said edge strength of said object pixel with respective values of edge strength derived for pixels disposed adjacent to said object pixel.
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Abstract
An image recognition apparatus operates on data of a color image to obtain an edge image expressing the shapes of objects appearing in the color image, the apparatus including a section for expressing the color attributes of each pixel of the image as a color vector, in the form of a set of coordinates of an orthogonal color space, a section for applying predetermined arrays of numeric values as edge templates to derive for each pixel a number of edge vectors each corresponding to a specific edge direction, with each edge vector obtained as the difference between weighted vector sums of respective sets of color vectors of two sets of pixels which are disposed symmetrically opposing with respect to the corresponding edge direction, and a section for obtaining the maximum modulus of these edge vectors as a value of edge strength for the pixel which is being processed. By comparing the edge strength of a pixel with those of immediately adjacent pixels and with a predetermined threshold value, a decision can be reliably made for each pixel as to whether it is actually located on an edge and, if so, the direction of that edge.
36 Citations
47 Claims
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1. An image recognition method of processing image data of a color image which is represented as respective sets of color attribute data of an array of pixels, to successively operate on each of said pixels as an object pixel for thereby determining whether said object pixel is located on an edge within said color image, and thereby derive shape data expressing an edge image corresponding to said color image, the method comprising steps of:
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expressing said sets of color attribute data of each of said pixels as respective color vectors, with each said color vector defined by a plurality of scalar values which are coordinates of an orthogonal color space;
for each of a plurality of predetermined edge directions, generating a corresponding edge template as an array of respectively predetermined numeric values;
extracting an array of color vectors a respective color vectors of an array of said pixels, said array of pixels being centered on said object pixel;
successively applying each of said edge templates to said array of color vectors in a predetermined array processing operation, to derive edge vectors respectively corresponding to said edge directions;
comparing the respective moduli of said derived edge vectors to obtain a value of edge strength for said object pixel, as a maximum value of modulus of said edge vectors, and obtaining a possible edge direction for said object pixel as a direction corresponding to an edge vector having said maximum value of modulus; and
judging whether said object pixel is located on an actual edge which is oriented in said possible edge direction, based upon comparing said edge strength of said object pixel with respective values of edge strength derived for pixels disposed adjacent to said object pixel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 23, 24)
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15. A method of deriving for a selected pixel of a color image which is formed of an array of pixels, for each of a plurality of predetermined edge directions, an edge strength value which corresponds to a specific one of a plurality of predetermined edge directions and is indicative of a degree of probability that said selected pixel is located on an edge between regions of respectively different color within said image, with said edge being oriented in said specific edge direction, the method comprising a set of steps performed for each of said edge directions of:
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expressing the color attributes of each of said pixels of said color image as a plurality of scalar values representing a color vector within an orthogonal color space;
obtaining a first weighted vector sum of a first set of pixels which are located adjacent to said selected pixel on one side thereof with respect to said specific edge direction and a second weighted vector sum of a second set of pixels which are located adjacent to said selected pixel on an opposite side from said first set with respect to said specific edge direction, and deriving the vector difference between said first and second weighted vector sums; and
obtaining the modulus of said vector difference, and a step of judging the respective moduli thereby obtained respectively corresponding to said predetermined edge directions, to obtain said edge strength value as the largest one of said moduli.
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16. An image recognition method for operating on shape data expressing an original region image to obtain shape data expressing a region image in which specific small regions have been eliminated, comprising repetitive execution of a series of steps of:
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selectively determining respective regions of said original region image as constituting a set of small regions which are each to be subjected to a region combining operation;
selecting one of said set of small regions as a next small region which is to be subjected to said region combining operation;
for each of respective regions which are disposed immediately adjacent to said next small region, calculating a length of common boundary line with respect to said next small region, and determining one of said immediately adjacent regions which has a maximum value of said length of boundary line; and
combining said next small region with said adjacent region having the maximum length of common boundary line. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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25. An image recognition apparatus for processing image data of a color image which is represented as respective sets of color attribute data of an array of pixels, to successively operate on each of said pixels as an object pixel for thereby determining whether said object pixel is located on an edge within said color image, and thereby derive shape data expressing an edge image corresponding to said color image, the apparatus comprising:
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color vector generating means for expressing said sets of color attribute data of each of said pixels as respective color vectors, with each said color vector in the form of an array of a plurality of scalar values which are coordinates of an orthogonal color space;
edge template application means for generating a plurality of edge templates each formed of an array of respectively predetermined numeric values, with said edge templates corresponding to respective ones of a plurality of predetermined edge directions, for extracting an array of color vectors as respective color vectors of an array of said pixels, with said array of pixels centered on said object pixel, and successively applying each of said edge templates to said array of color vectors in a predetermined array processing operation, to derive edge vectors respectively corresponding to said edge directions;
edge pixel determining means for comparing the respective moduli of said derived edge vectors to obtain a value of edge strength for said object pixel, as a maximum value of modulus of said edge vectors, for obtaining a possible edge direction for said object pixel as a direction corresponding to an edge vector having said maximum value of modulus, and for judging whether said object pixel is located on an actual edge which is oriented in said possible edge direction, based upon comparing said edge strength of said object pixel with respective values of edge strength derived for pixels disposed adjacent to said object pixel. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 46, 47)
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39. An image recognition apparatus for operating on shape data expressing an original region image to obtain shape data expressing a region image in which specific small regions have been eliminated, comprising:
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small region detection means for selectively determining respective regions of said original region image as constituting a set of small regions which are each to be subjected to region combination;
region combination determining means for selecting one of said set of small regions as a next small region which is to be subjected to said region combination; and
,region combining means for calculating respective values of common boundary line between said next small region and each of the regions which are located immediately adjacent to said next small region, for determining one of said immediately adjacent regions which has a maximum value of said length of boundary line, and for combining said next small region with said adjacent region having the maximum length of common boundary line. - View Dependent Claims (40, 41, 42, 43, 44, 45)
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Specification