R/onload.R

In tesseract: Open Source OCR Engine

.onLoad <- function(lib, pkg){
  pkgdir <- file.path(lib, pkg)
  version <- tesseract_version_major()
  appname <- ifelse(version < 4, "tesseract", paste0("tesseract", version))
  sysdir <- rappdirs::user_data_dir(appname)
  pkgdata <- normalizePath(file.path(pkgdir, "tessdata"), mustWork = FALSE)
  sysdata <- normalizePath(file.path(sysdir, "tessdata"), mustWork = FALSE)
  if(!is_testload() && file.exists(pkgdata) && !file.exists(file.path(sysdata, "eng.traineddata"))){
    dir.create(sysdir, showWarnings = FALSE, recursive = TRUE)
    if(file.exists(sysdir)){
      onload_notify()
      olddir <- getwd()
      on.exit(setwd(olddir))
      setwd(pkgdir)
      file.copy("tessdata", sysdir, recursive = TRUE)
    }
  }
  if(is.na(Sys.getenv("TESSDATA_PREFIX", NA))){
    if(file.exists(file.path(sysdata, "eng.traineddata"))){
      Sys.setenv(TESSDATA_PREFIX = sysdata)
    } else if(file.exists(file.path(pkgdata, "eng.traineddata"))){
      Sys.setenv(TESSDATA_PREFIX = pkgdata)
    }
  }

  if(grepl('tesseract.Rcheck', getwd(), fixed = TRUE)){
    Sys.setenv(OMP_THREAD_LIMIT=2)
    Sys.setenv(OMP_NUM_THREADS=2)
  }
}

tesseract_version_major <- function(){
  as.numeric(substring(tesseract_config()$version, 1, 1))
}

onload_notify <- function(){
  message("First use of Tesseract: copying language data...\n")
}

is_testload <- function(){
  as.logical(nchar(Sys.getenv("R_INSTALL_PKG")))
}

.onUnload <- function(lib){
  Sys.unsetenv("TESSDATA_PREFIX")
}

.onAttach <- function(lib, pkg){
  check_training_data()

  # Load tibble (if available) for pretty printing
  if(interactive() && is.null(.getNamespace('tibble'))){
    tryCatch({
      getNamespace('tibble')
    }, error= function(e){})
  }
}

check_training_data <- function(){
  tryCatch(tesseract(), error = function(e){
    warning("Unable to find English training data", call. = FALSE)
    os <- utils::sessionInfo()$running
    if(isTRUE(grepl("ubuntu|debian", os, TRUE))){
      stop("DEBIAN / UBUNTU: Please run: apt-get install tesseract-ocr-eng")
    }
  })
}