R/jpeg_roll.R

In hathawayj/cards: Build's flash cards from BYU-I picture roll

#'	@title Pictorial Class Roll to by student
#'	@param plot_color plot the color shading values for the pixels while data is being digested in the function. Defaults to TRUE
#'	@param image_files the image files that are to be converted
#'	@notes requires the jpeg package
#' 	@example pdata <- jpeg_roll()
#'	@export
jpeg_roll <-  function(image_files, plot_color = TRUE){

  # Set-up empty vectors
  all_names <-  vector("list",length(image_files))
  all_faces <-  vector("list",length(image_files))
  names(all_names) <-  gsub(".jpg","",image_files)
  names(all_faces) <-  gsub(".jpg","",image_files)

  for (files in image_files){
    class = jpeg::readJPEG(files)
    # rows are multiple pixels
    average_color_row = apply(class[,, 3], 1, mean)
    row_lines3 = c(1:nrow(class))[average_color_row < min(average_color_row) + .035]
    row_lines = c(row_lines3[diff(row_lines3) != 1], row_lines3[length(row_lines3)])

    average_color_column = apply(class[,,3], 2, mean)
    col_lines3 = c(1:ncol(class))[average_color_column < min(average_color_column) + .035]
    if(plot_color == TRUE) plot(c(apply(class[,,3], 1, mean), apply(class[,,3], 2, mean)))
    col_lines = c(col_lines3[diff(col_lines3) != 1], col_lines3[length(col_lines3)])


    students = vector("list", length = (length(row_lines) - 1)*(length(col_lines) - 1))
    students_picture = vector("list",length = (length(row_lines) - 1)*(length(col_lines) - 1))

    loc = 1
    for (i in 1:c(length(row_lines) - 1)) {
      print(i)
      rows = row_lines[i]:row_lines[i + 1]
      rows_picture = row_lines[i]:c(row_lines[i] + 420)
      for (j in 1:c(length(col_lines) - 1)) {
        #print(j)
        #print(loc)
        students[[loc]] = class[rows, col_lines[j]:col_lines[j + 1],] # picture with text
        students_picture[[loc]] = class[rows_picture, col_lines[j]:col_lines[j + 1],]    # picture only
        loc = loc + 1
      } # end j
    } # end i

    all_names[[gsub(".jpg","",files)]] = students
    all_faces[[gsub(".jpg","",files)]] = students_picture

    print(files)
  }
  list(all_names = all_names,all_faces = all_faces)

}  # end funtion