R/MakeTransparent.R

In sascha2schroeder/popEye: Analysis of eye-tracking data from reading experiments

MakeTransparent = function(..., alpha=0.5) {
  
  if(alpha<0 | alpha>1) stop("alpha must be between 0 and 1")
  
  alpha = floor(255*alpha)  
  newColor = col2rgb(col=unlist(list(...)), alpha=FALSE)
  
  .makeTransparent = function(col, alpha) {
    rgb(red=col[1], green=col[2], blue=col[3], alpha=alpha, maxColorValue=255)
  }
  
  newColor = apply(newColor, 2, .makeTransparent, alpha=alpha)
  
  return(newColor)
  
}