An image similarity measure based on graph matching

The problem of computing the similarity between two images is transformed to that of approximating the distance between two extended region adjacency graphs, which are extracted from the images in time and space linear in the number of pixels. Invariance to translation and rotation is thus achieved. Invariance to scaling is also achieved by taking the relative size of regions into account. Furthermore, the method provides a trade-off between pixel similarity threshold and approximation of the distance measure, which can be used to bound the error in image recognition as well as the time complexity of the computation