# 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
"add.image" <- function(xpos, ypos, z, adj.x = 0.5, 
    adj.y = 0.5, image.width = 0.15, image.height = NULL, col = tim.colors(256), 
    ...) {
    m <- nrow(z)
    n <- ncol(z)
    ucord <- par()$usr
    pin <- par()$pin
    # if height is missing scale according to width assuming pixels are
    # square.
    if (is.null(image.height)) {
        image.height <- (n/m) * image.width
    }
    # find grid spacing in user coordinates.
    dy <- image.width * (ucord[4] - ucord[3])
    dx <- image.height * pin[2] * (ucord[2] - ucord[1])/(pin[1])
    #
    # dx and dy should have the correct ratio given different different scales
    # and also different aspects to the plot window
    #
    # find grid to put image in right place.
    xs <- seq(0, dx, , m + 1) + xpos - adj.x * dx
    ys <- seq(0, dy, , n + 1) + ypos - adj.y * dy
    image(xs, ys, z, add = TRUE, col = col, ...)
}