naive image filter

filterImage <- function(imgArray, imgFilter) {
  x <- dim(imgArray)[1]
  y <- dim(imgArray)[2]
  z <- dim(imgArray)[3]

  dx <- floor(dim(imgFilter)[1] / 2)
  dy <- floor(dim(imgFilter)[2] / 2)

  newImgArray <- array(0, dim = c(x, y, z))
  for (i in 1:x) {
    for (j in 1:y) {
      for (k in 1:z) {
        for (p in (0 - dx):(0 + dx)) {
          for (q in (0 - dy):(0 + dy)) {
            if (i + p < 1 || i + p > x || j + q < 1 || j + q > y) {
              next
            }
            newImgArray[i, j, k] <- newImgArray[i, j, k] +
              imgArray[(i + p), (j + q), k] * imgFilter[dx + p + 1, dy + q + 1]
          }
        }
      }
    }
  }
  newImgArray
}

library('png')
imgFilter <- array(1/9, dim=c(3, 3)) # mean filter
rawImageArray <- readPNG('background.png')
filteredImageArray <- filterImage(rawImageArray, imgFilter)
writePNG(filteredImageArray, target = 'backgroundFiltered.png')