US 5,845,007 A · Machine vision method and apparatus for edge-based image histogram analysis

Abstract

A system for edge-based image histogram analysis permits identification of predominant characteristics of edges in an image. The system includes an edge detector that generates an edge magnitude image having a plurality of edge magnitude values based on pixels in the input image. The edge detector can be a Sobel operator that generates the magnitude values by taking the derivative of the input image values, i.e., the rate of change of intensity over a plurality of image pixels. A mask generator creates a mask based upon the values output by the edge detector. The mask can be used for masking input image values that are not in a region for which there is a sufficiently high edge magnitude. A mask applicator applies the pixel mask array to a selected image, e.g., the input image or an image generated therefrom (such as an edge direction image of the type resulting from application of a Sobel operator to the input image). A histogram generator generates a histogram of the pixel values in the masked image, i.e., a count of the number of image pixels that pass through the mask. A peak detector identifies the intensity value in the histogram that represents the predominant image intensity value (image segmentation threshold) or predominant edge direction values associated with the edge detected by the edge detector.

Claims17

Dependent claims

An apparatus for determining a characteristic of an edge represented in an input image that includes a plurality of input image pixels, the apparatus comprising:

edge magnitude detection means for generating an edge magnitude image including a plurality of edge magnitude pixels, each having a value that is indicative of a rate of change of a plurality of values of respective input image pixels;
mask generating means, coupled with the edge magnitude detection means, for generating an array of pixel masks, each having a value that is masking or non-masking and that is dependent on a value of one or more respective edge magnitude pixels;
mask applying means, coupled to the mask generating means, for generating a masked image including only those pixels from a selected image that correspond to non-masking values in the array;
histogram means, coupled to the mask applying means, for generating a histogram of pixels in the masked image;
and
peak detection means, coupled with the histogram means, for identifying in the histogram at least one value indicative of a predominant characteristic of an edge represented in the input image and for outputting a signal representing that value.

3 more elements

A method for determining a characteristic of an edge represented in an input image that includes a plurality of input image pixels, the method comprising:

an edge magnitude detection step for generating an edge magnitude image including a plurality of edge magnitude pixels, each having a value that is indicative of a rate of change of one or more values of respective input image pixels;
a mask generating step for generating an array of pixel masks, each having a value that is masking or non-masking and that is dependent on a value of one or more respective edge magnitude pixels;
a mask applying step for generating a masked image including only those pixels from a selected image that correspond to non-masking values in the array;
a histogram step for generating a histogram of pixels in the masked image;
and
a peak detection step for identifying in the histogram a value indicative of a predominant characteristic of an edge represented in the input image and for outputting a signal representing that value.

3 more elements

Dependencies are inferred from the claim text.

Machine vision method and apparatus for edge-based image histogram analysis

Life of this patent

Machine vision method and apparatus for edge-based image histogram analysis

Life of this patent

Abstract

Claims17