adding new functionality suggested in #107

DESCRIPTION

@@ -15,7 +15,9 @@ Authors@R: c(person("Thomas J.", "Leeper",
                     comment = "rOpenSci reviewer"),
              person("Lincoln", "Mullen",
                     role = "ctb",
-                    comment = "rOpenSci reviewer"))
+                    comment = "rOpenSci reviewer"),
+             person("Thore", "Engel",
+                    role = "ctb"))
 Maintainer: Tom Paskhalis <[email protected]>
 Description: Bindings for the 'Tabula' <http://tabula.technology/> 'Java'
     library, which can extract tables from PDF documents. The 'tabulizerjars'
@@ -41,4 +43,4 @@ Suggests:
     testthat
 SystemRequirements: Java (>= 7.0)
 VignetteBuilder: knitr
-RoxygenNote: 6.0.1
+RoxygenNote: 6.1.1

NAMESPACE

@@ -7,6 +7,7 @@ export(extract_text)
 export(get_n_pages)
 export(get_page_dims)
 export(locate_areas)
+export(locate_columns)
 export(make_thumbnails)
 export(merge_pdfs)
 export(split_pdf)

NEWS.md

@@ -1,8 +1,11 @@
+
+
 # CHANGES TO tabulizer 0.2.2
 
 * `extract_tables()` gets `outdir` argument for writing out CSV, TSV and JSON
 files.
 * Fixes in vignette.
+* addition of `locate_columns()` function.
 
 # CHANGES TO tabulizer 0.2.1
 

R/locate_columns.R

@@ -0,0 +1,108 @@
+
+#' Locate separators between columns
+#'
+#' This function allows the user to manually locate the separators between columns of a table in a pdf. The output can be used as the \code{columns} argument in \code{extract_tables()}
+#' 
+#' Manually selecting the separators can ensure that values stay in their respective columns. This is useful when some rows of a table have no or only little white space between columns. The code is an adaptation of the \code{locate_area()} function and its helpers.
+#' @param file A character string specifying the path or URL to a PDF file.
+#' @param pages An optional integer vector specifying pages to extract from.
+#' @param resolution An integer specifying the resolution of the PNG images conversions. A low resolution is used by default to speed image loading.
+#' @param copy Specifies whether the original local file(s) should be copied to tempdir() before processing. FALSE by default. The argument is ignored if file is URL.
+#' @return a list.
+#' @author Thore Engel <[email protected]>  
+#' @export
+#'
+#' @examples
+#' \donttest{
+#' f <- system.file("examples", "data.pdf", package = "tabulizer")
+#' separators<-locate_columns(f, pages= 1 )
+#' extract_tables(f,pages = 1, columns = separators[1])
+#' }
+#' 
+locate_columns <- function(file,
+                         pages = NULL,
+                         resolution = 60L,
+                         copy = FALSE) {
+    if (!interactive()) {
+        stop("locate_columns() is only available in an interactive session")
+    } else {
+        requireNamespace("graphics")
+        requireNamespace("grDevices")
+    }
+
+    file <- localize_file(file, copy = copy)
+    # on.exit(unlink(file), add = TRUE)
+    dims <- get_page_dims(file, pages = pages)
+    paths <- make_thumbnails(file,
+                             outdir = tempdir(),
+                             pages = pages,
+                             format = "png",
+                             resolution = resolution)
+    on.exit(unlink(paths), add = TRUE)
+
+    separators <- rep(list(NULL), length(paths))
+    i <- 1
+    warnThisTime <- TRUE
+    while (TRUE) {
+        if (!is.na(paths[i])) {
+            a <- try_columns_reduced(file = paths[i], 
+                          dims = dims[[i]],warn = warnThisTime)
+            if(warnThisTime) warnThisTime <- F
+            if (!is.null(a[["separators"]])) {
+                separators[[i]] <- a[["separators"]]
+            }
+            if (tolower(a[["key"]]) %in% c("del", "delete", "ctrl-h")) {
+                separators[i] <- list(NULL)
+                next
+            } else if (tolower(a[["key"]]) %in% c("home")) {
+                i <- 1
+                next
+            } else if (tolower(a[["key"]]) %in% c("end")) {
+                i <- length(paths)
+                next
+            } else if (tolower(a[["key"]]) %in% c("pgup", "page_up", "up", "left")) {
+                i <- if (i == 1) 1 else i - 1
+                next
+            } else if (tolower(a[["key"]]) %in% c("q")) {
+                break
+            }
+        }
+        i <- i + 1
+        if (i > length(paths)) {
+            break
+        }
+    }
+    return(separators)
+}
+
+
+#' Helper function to locate_columns()
+#'
+#' @param file A character string specifying the path or URL to a PDF file.
+#' @param dims An integer specifying the resolution of the PNG images conversions. A low resolution is used by default to speed image loading.
+#' @param warn Display warning?
+
+try_columns_reduced <- function(file, dims, warn = FALSE) {
+    if (warn) {
+        message("Click at the locations of separators between columns.")
+    }
+    if (grDevices::dev.capabilities()[["rasterImage"]] == "no") {
+        stop("Graphics device does not support rasterImage() plotting")
+    }
+    thispng <- readPNG(file, native = TRUE)
+    drawPage <- function() {
+        graphics::plot(c(0, dims[1]), c(0, dims[2]), type = "n", xlab = "", ylab = "", asp = 1)
+        graphics::rasterImage(thispng, 0, 0, dims[1], dims[2])
+    }
+
+    pre_par <- graphics::par(mar=c(0,0,0,0), xaxs = "i", yaxs = "i", bty = "n")
+    on.exit(graphics::par(pre_par), add = TRUE)
+    drawPage()
+    on.exit(grDevices::dev.off(), add = TRUE)
+
+    tmp <- locator()
+    graphics::abline(v=tmp$x)
+    Sys.sleep(4)
+    separators= as.numeric(tmp$x)
+    return(list(key = "right", separators = separators))
+}