# fields, Tools for spatial data
# Copyright 2004-2007, Institute for Mathematics Applied Geosciences
# University Corporation for Atmospheric Research
# Licensed under the GPL -- www.gpl.org/licenses/gpl.html
"Wimage.cov" <- function(Y = NULL, ind = NULL, H.obj, 
    find.row = FALSE) {
    # local multipcation by H function
    Mult.H <- function(u, H.obj) {
        IND <- H.obj$ind0
        u[IND] <- H.obj$H0 %*% c(u[IND])
        u * H.obj$H1
    }
    #
    # This is a shortcut option to find a single row of the covariance matrix
    #
    if (find.row) {
        Y <- 1
    }
    #
    # if ind is  passed fill complete image with the Y subset
    #
    if (is.null(ind)) {
        tmp <- Y
    }
    else {
        tmp <- matrix(0, nrow = H.obj$m, ncol = H.obj$n)
        tmp[ind] <- Y
    }
    #
    #
    hold <- Wtransform.image(tmp, cut.min = H.obj$cut.min, inv = TRUE, 
        transpose = TRUE)
    #
    hold <- Mult.H(hold, H.obj = H.obj)
    # multiplication by transpose.
    hold <- Mult.H(hold, H.obj = H.obj)
    Wtransform.image(hold, cut.min = H.obj$cut.min, inv = TRUE)
}