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I have a directory full of 100 .png images I'd like to convert to pdf.

The images are exactly the size I want the pdf to be.

I can create a multi-page pdf using magick "manually" like this:

library(magick)

img1 <- image_read("image1.png")
img2 <- image_read("image2.png")

image_write(c(img1, img2), format = "pdf", "check.pdf")

But I'm having trouble getting the image_write command to accept a vector of filenames to automate this process. For example, I'd like to make a 100-page pdf from the .png images in my directory "test":

all_images <- list.files("test")

I thought that purrr might help but no luck:

library(purrr)

image_write(map(all_images, image_read), format = "pdf", "check.pdf")

Any ideas?

lobati
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Nova
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2 Answers2

2

You need to concatenate different "magick-image objects using c.

It's the same as doing c(img1,img2,img3,...)

all_images_1 <- purrr::reduce(
    purrr::map(all_images,image_read),
    c
)

image_write(all_images_1 , format = "pdf", "check.pdf")
yusuzech
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    Isn't `image_read` vectorized? So all that's needed is `image_write(image_read(all_images), format = "pdf", "file.pdf")` – Brian Sep 13 '19 at 07:01
  • Brian, of course, this worked for me this morning, but not last night. I kept getting errors that things "were not magick objects". Thanks. – Nova Sep 13 '19 at 11:03
  • Brian if you want to add that as an answer I will shamefully accept it... I swear I did try that!! – Nova Sep 13 '19 at 11:18
2

magick::image_*() functions are vectorized. So you can do:

dir = '/path/to/dir'
fl = list.files(dir, full.names = TRUE, pattern = '.png')
# magick
img = image_read(fl) # read from vector of paths
img2 = image_append(img, stack = TRUE) # places pics above one another

image_write(img2, file.path(dir, 'check.pdf'))

This places the images above one another, yet not on single pages.

andschar
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