# 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

"D4transform.image" <-
function (x, inv = FALSE, transpose = FALSE, cut.min = 8) 
{
    if (transpose) 
        inv <- !inv
    n <- dim(x)[1]
    m <- dim(x)[2]
    if (n > m) {
        flip <- TRUE
        temp <- t(x)
        n <- dim(temp)[1]
        m <- dim(temp)[2]
    }
    else {
        flip <- FALSE
        temp <- x
    }
    if (n > m) 
        stop(" number of columns of x must >= to number of\nrows")
    nn <- n
    mm <- m
    if (!inv) {
        while (nn > cut.min) {
            temp[1:nn, 1:mm] <- WD42d(temp[1:nn, 1:mm])
            nn <- nn/2
            mm <- mm/2
        }
    }
    if (inv) {
        NN <- n
        MM <- m
        while (NN > cut.min) {
            NN <- NN/2
            MM <- MM/2
        }
        nn <- NN * 2
        mm <- MM * 2
        while (nn <= n) {
            temp[1:nn, 1:mm] <- WD42di(temp[1:nn, 1:mm])
            nn <- nn * 2
            mm <- mm * 2
        }
    }
    if (flip) {
        return(t(temp))
    }
    else {
        return(temp)
    }
}