METHOD AND APPARATUS FOR DERIVING A PERCEPTUAL HASH VALUE FROM AN IMAGE

摘要

A method and apparatus for deriving a hash value from a single channel image, comprising: size reducing the image into first resized images having different horizontal and vertical size, deriving therefrom horizontal difference images comprising horizontal neighboring pixel differences, size reducing the image into second resized images having different horizontal and vertical size, deriving therefrom vertical difference images comprising vertical neighboring pixel differences, and combining the sign bits of the horizontal neighboring pixel differences and the sign bits of the vertical neighboring pixel differences in a predefined order into bits of the hash value.

主权项

1. A method for converting a single channel image of arbitrary size into a fixed bit length hash value that allows similarity comparisons, the method comprising:
size reducing the image into a series comprising a number n of first resized images having different horizontal and vertical size and deriving from each first resized image a horizontal difference image comprising horizontal neighboring pixel differences, wherein the horizontal size and the vertical size of the first resized images are chosen such that the total number of horizontal neighboring pixel differences is constant for all horizontal difference images, size reducing the image into a series comprising the same number n of second resized images having different horizontal and vertical size and deriving from each second resized image a vertical difference image comprising vertical neighboring pixel differences, wherein the horizontal size and the vertical size of the second resized image are chosen such that the total number of vertical neighboring pixel differences is constant for all vertical difference images, wherein the method further comprises: combining the sign bits of the horizontal neighboring pixel differences of all horizontal difference images and the sign bits of the vertical neighboring pixel differences of all vertical difference images, in a predefined order, into bits of the hash value.