1. A quantization method for enhancing an image, comprising: (a) providing a vector c of frame expansion coefficients c j for an input signal, where the c j are expressed as multiples of a quantization step size; (b) computing a vector of truncation errors e where for each coefficient e j =c j −floor(c j ), where floor(c j ) denotes the integer part of c j ; (c) computing e R =B(e), where B is a projection onto a subspace of vectors of possible expansion coefficients; (d) initializing a binary vector α as the 0 vector and provide M clusters of vectors in said subspace where said clusters are of correlated vectors and a j-th cluster has representative vector h j and binary increment vector μ j ; (d) for j=1, 2,. .. , M: when ∥e R +h j ∥<∥e R ∥, updating e R to e R +h j and update α to α±μ j ; (e) repeating step (d) until there are no more updates; and (f) outputing for each coefficient c j the sum floor(c j )+α j ; (g) utilizing the outputted sum floor(c j )+α j for each coefficient c j in quantization, wherein said quantization produces an enhanced image.