R/Morton_combine.R

In rwoldford/glyphs: Make glyphs using pixel-oriented data visualization technique

library(png)
library(pixmap)

#' @title  Morton curve data visualization
#' @description MortonGlyph generates a data matrix of png format or a class of "pixmap" which can be used to display color strings in an order of Morton curve in the space given a vector of colors
#' @param col vector of colors
#' @param fill logical value indicating whether the color strings repeat from the beginning if number of colors is smaller than the total length of Morton curve
#' @param type string specifying the format of output. "png" means the output is a data matrix in the png format, and "pixmap" means the output is a class of pixmap.
#' @return a data matrix of png format or a class of "pixmap" which can be used to plot. See \code{\link[pixmap]{pixmap}}, \code{\link[png]{writePNG}}, \code{\link[graphics]{rasterImage}}
#' @author Jiahua Liu, Wayne Oldford
#' @examples
#' myPngmat <- MortonGlyph()
#' myPngmat <- MortonGlyph(col = colors())
#' myPngmat <- MortonGlyph(col = colors(), fill = TRUE)
#' writePNG(myPngmat, target = "myplot.png")
#' plot(0,type='n', xlim=c(0,1), ylim=c(0,1), axes = FALSE, xlab = "", ylab = "")
#' rasterImage(myPngmat,0,0,1,1)
#' mypixmap <- MortonGlyph(type = "pixmap")
#' mypixmap <- MortonGlyph(col = colors(), fill = TRUE, type = "pixmap")
#' plot(mypixmap)
#' 
#' @export


MortonGlyph <- function(col, fill = FALSE, type = c("png","pixmap")){
  oldw <- getOption("warn")
  options(warn = -1)
  type <- match.arg(type)
  if(missing(col)) col <- rainbow(64)  # an example
  levels <- 1:13
  level <- levels[findInterval(length(col),2^(2*levels),left.open = TRUE)+1]
  if(level >= 13) stop("Too many colors to display")
  maxLength <- 2^(2*level)
  sideLength <- 2^level
  if (fill){
    if(length(col) <= maxLength) {
      col <- rep_len(col, length.out = maxLength)
    }
  }
  switch(type,
         png = {
           size <- ceiling(480/sideLength)
           png_mat <- array(dim = c(size*sideLength,size*sideLength,4))
           col_mat <- matrix(0,nrow = 4,ncol = maxLength)
           col_mat[,1:min(maxLength,length(col))] <- col2rgb(col,alpha = TRUE)[,1:min(maxLength,length(col))]/255
           pngFn <- function(x, y, col) {
             for(i in 1:size){
               for(j in 1:size){
                 png_mat[size*y+i,size*x+j,] <<- col
               }
             }
           }
           locNum <- 1
           SetPixel <- function(x, y,col_mat){
             pngFn(x,y, col = col_mat[,locNum])
             locNum <<- locNum+1
           }
           col <- col_mat
         },
         pixmap = {
           pix_col <- character(maxLength)
           pixFn <- function(x, y, num, col) {
             index <- x*2^level + y + 1
             pix_col[index] <<- col
           }
           locNum <- 1
           SetPixel <- function(x,y,col){
             pixFn(x, y, locNum, col = col[locNum])
             locNum <<- locNum + 1
           }
         }
  )
  MortonStep <- function(x,y,level,col){
    if (level>1){
      MortonStep(x,y,level-1,col)
      MortonStep(x+2^(level-1),y,level-1,col)
      MortonStep(x,y+2^(level-1),level-1,col)
      MortonStep(x+2^(level-1),y+2^(level-1),level-1,col)
    }
    else{
      SetPixel(x, y, col)
      SetPixel(x+1, y, col)
      SetPixel(x, y+1, col)
      SetPixel(x+1, y+1, col)
    }
  }
  MortonStep(0, 0, level, col)
  switch(type,
         png = {
           result <- png_mat
         },
         pixmap = {
           result <- pixmap::pixmapIndexed(1:maxLength, nrow=2^level, col=pix_col)
         })
  options(warn = oldw)
  return(result)
}