ghostpdf

Ghostpdf wraps around ghostscript to provide easy manipulation functions for pdf files. With Ghostpdf you can merge documents, decrypt them, encrypt them back, transform pdfs into images or extract pages from a pdf.

Note The idea is to eventually have the same functions applicable with PostScript files too.

Installation

You can install the development version of ghostpdf from GitHub with:

# install.packages("devtools")
devtools::install_github("RodrigoZepeda/ghostpdf")

You will also need to install ghostpdf either from their page https://www.ghostscript.com/releases/gsdnld.html or if you are in a Unix system with a package manager such as:

• OSX brew install ghostscript
• Ubuntu/Debian sudo apt-get install ghostscript
• CentOS/Fedora sudo yum install ghostscript

OSX users who are not familiar with homebrew open terminal and copy:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

after the installation is completed, reopen the terminal and write:

brew install ghostscript

Examples

library(ghostpdf)

#We'll generate some pdf documents for the examples
colors <- rainbow(9)
for (i in 1:9){
  pdf(paste0("Example",i,".pdf"), width = 6, height = 4)
  plot(x = rnorm(100), y = rnorm(100), col = colors[i], main = paste0("Page ", i))
  dev.off()
}

Merging pdfs

You can merge multiple pdf files into a single file:

#Merge them
pdf_merge(output_file = "All_pdfs.pdf")
#> NULL

#Or merge some of them:
pdf_merge(c("Example1.pdf", "Example6.pdf"), output_file = "Some_pdfs.pdf")
#> NULL

Extracting pages from a pdf

One can extract some of the pages from a pdf:

#Extract from page 2 to 4
pdf_extract("All_pdfs.pdf", first_page = 2, last_page = 4, 
            output_file = "All_pdfs_subset.pdf")

#Or pages 1, 5 and 8
pdf_extract("All_pdfs.pdf", page_sequence = c(1,5,8),
          output_file = "Other_pdfs_subset.pdf")

Shrinking a pdf

You can reduce the size of a pdf with pdf_shrink which enables compression and other memory-saving tricks:

#Check current file size:
original_size <- file.info("All_pdfs_subset.pdf")["size"]

#Shrink file
pdf_shrink("All_pdfs_subset.pdf")
#> NULL

#Check new file size
reduced_size <- file.info("All_pdfs_subset.pdf")["size"]

#Verify size is smaller
#in this case there isn't much to gain because the pdf was small by itself
#in large pdfs this is useful
message(paste0("Shrank pdf from ", original_size, " to ", reduced_size))
#> Shrank pdf from 29518 to 27350

PDF to image

Transform a pdf (or select) into images in any of the following formats: png, tiff, jpeg, fax, pcx, bmp, psd:

#Transform a pdf into png
pdf_to_image("Some_pdfs.pdf", output_file = "cool_plots.png")

#Or sections of another pdf
pdf_to_image("All_pdfs.pdf", first_page = 4, last_page = 7, output_file = "cooler_plots.jpg")

#Sections can also be specified with a vector
pdf_to_image("All_pdfs.pdf", page_sequence = c(1,5,8,9), 
             output_file = "cooler_plots.tiff")

#You can also specify the imagedevice for example to grayscale
pdf_to_image("All_pdfs.pdf", page_sequence = c(1:4, 7),
             image_device = "pnggray",
             output_file = "gray_plots.png")

#Additional options can be passed in additional_flags e.g. transparent background
pdf_to_image("All_pdfs.pdf", page_sequence = 2,
             image_device = "pngalpha",
             output_file = "nbg.png",
             additional_flags = c("-dBackgroundColor=16#fffff",
                                  "-dDownScaleFactor=3"))

Encrypt / decrypt pdf

You can encrypt a pdf file with:

pdf_encrypt("Example1.pdf", password = "mypassword")
#> NULL

To create a decrypted copy:

pdf_decrypt("Example1.pdf", password = "mypassword")
#> NULL

More

I would like to eventually add same functionality for eps files and to transform between images and image to pdf.

Troubleshooting

• Can’t find ghostscript on windows
  1. I would recommend executing R as administrator. That’s the easier (unsafe) way.
  2. Open cmd and write where gswin64c or where gswin32c. One of them should work. The path returned has to be used as gs_path in functions:

pdf_merge(output_file = "All_pdfs.pdf", gs_path = "C:/Program Files/gs/gs9.56.1/bin/gswin64c.exe")