getClass(, package=pixmap)
pixmapIndexed


plot(p1 <- pixmapIndexed(matrix(0, nrow=3, ncol=4), col=))


cols <- rep(, 12); cols[7] <- 
plot(p2 <- pixmapIndexed(matrix(1:12, nrow=3, ncol=4), col=cols))


getcol <- function(pm, i, j)
{
   pmcol <- pm@col
   dim(pmcol) <- dim(pm@index)
   pmcol[i,j]   
}
getcol(p2, 3, 4)