Image recognition edge detection method and system

Claim 1

In a system in which an image frame formed of a two dimensional array of pixels is represented by a plurality of gray scale values, each gray scale value representing a gray scale of a separate pixel in the image frame, means for determining the edges of an object in the image frame, comprising: reference determining means for establishing a reference contract level based on the distribution of differences between gray scale and values of pairs of contiguous pixels in the image frame said reference determining means comprising means for examining the distribution of differences between gray scale values of pair of contiguous pixels, and establishing as the reference contrast level the difference level which is the last of a predetermined number of successive difference levels each of which exceeds the next smaller difference level by at least a predetermined amount, said reference determining means comprising additional means for examining groups of gray scale values, the groups corresponding to square groupings of four contiguous pixels, and, for each group, calculating the differences between every combination of pairs of gray scale values, said means for examining groups of gray scale values further determining the distribution of differences between gray scale values of pairs of contiguous pixels; and means for examining groups of gray scale values, the groups corresponding to square groupings of four contiguous pixels, and producing a two dimensional array of elements arranged to correspond to the arrangement of square groupings of four contiguous pixels, each element in the array having either a first or second value, the first value occurring only if the difference between gray scale values corresponding to a pair of pixels in a square grouping of four contiguous pixels is greater than the reference contrast level, whereby the first values are arranged to represent the edges of the object in the image frame.

Claim 4

A method for determining and representing the edges of an object in an image frame formed of a two dimensional array of pixels represented by a plurality of gray scale values, each gray scale value representing the gray scale of a separate pixel in the image frame, the method comprising the steps of: establishing a reference contrast level based on the distribution of differences between gray scale values of pairs on continuous pixels in the image frame, the step of establishing a reference contrast level comprising the steps of examining the distribution of differences between gray scale values and establishing as the reference contrast level the difference level which is the last of a predetermined number of successive difference levels each of which exceeds the next smaller difference level by at least a predetermined amount; examining groups of gray scale values corresponding to square groupings of four contiguous pixels, the step of examining the distribution of differences between gray scale values including the steps of examining groups of gray scale values corresponding to square groupings of four contiguous pixels, calculating for each group the differences between each combination of pairs of gray scale values, determining the distribution of differences in gray scale values in order of increasing difference, examining the distribution of differences in gray scale values for a plurality of successive difference levels, each of which exceeds the next smaller difference level by at least a predetermined amount and selecting the difference level which is the last of a predetermined number of difference levels in the succession as the reference contrast level; calculating for each group the differences between each combination of pairs of gray scale values; and producing a two dimensional array of elements arranged to correspond to the arrangement of square groupings of four contiguous pixels, each element in the array of elements having either a first or a second value, the first value occurring only if a difference between gray scale values of a pair of pixels in the corresponding square grouping is at least as great as the reference contrast level, whereby the first values are arranged to represent the edges of the object in the image frame.

Claim 5

A method for determining and representing the edges of an object in an image frame formed of a two dimensional array of pixels represented by a plurality of gray scale values, each gray scale value representing the gray scale of a separate pixel in the image frame, the method comprising the steps of: establishing a reference contrast level based on the distribution of differences between gray scale values of pairs on continuous pixels in the image frame, the step of establishing a reference contrast level comprising the steps of examining the distribution of differences between gray scale values and establishing as the reference contrast level the difference level which is the last of a predetermined number of successive difference levels each of which exceeds the next smaller difference level by at least a predetermined amount; examining groups of gray scale values corresponding to square groupings of four contiguous pixels, the step of examining the distribution of differences between gray scale values including the steps of examining groups of gray scale values corresponding to square groupings of four contiguous pixels, calculating for each group the differences between each combination of pairs of gray scale values, determining the distribution of differences in gray scale values in order of increasing difference, examining the distribution of differences in gray scale values for a plurality of successive difference levels, each of which exceeds the next smaller difference level by at least a predetermined amount and selecting the difference level which is the last of a predetermined number of difference levels in the succession as the reference contrast level; calculating for each group the differences between each combination of pairs of gray scale values; and producing a two dimensional array of elements arranged to correspond to the arrangement of square groupings of four contiguous pixels, each element in the array of elements having either a first or a second value, the first value occurring only if a difference between gray scale values of a pair of pixels in the corresponding square grouping is at least as great as the reference contrast level, whereby the first values are arranged to represent the edges of the object in the image frame.