Random crash during batch PDF to PNG conversion

[YulongNiu]

I would like to report an unexpected crash that occurs during the conversion of PDFs to PNGs. I have approximately 100 single-image PDF files, and the conversion process crashes unpredictably during the for loop iteration. I have manually verified that each PDF can be successfully converted to a PNG using the same code when run individually. The relevant code block is as follows:

for (i in PDFs) {
  eachPdf <- image_read_pdf(i, density = 300)
  eachPngPath <- ...
  image_write(eachPdf, path = eachPngPath, format = "png")
}

Error messages:

R: ../../magick/image.c:2285: ResetImagePixels: Assertion `image != (Image *) NULL' failed.
Aborted

sessionInfo:

> sessionInfo()
R version 4.5.1 (2025-06-13)
Platform: x86_64-pc-linux-gnu
Running under: Debian GNU/Linux 12 (bookworm)

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.11.0
LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.11.0  LAPACK version 3.11.0

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

time zone: Europe/Copenhagen
tzcode source: system (glibc)

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] magick_2.8.7

loaded via a namespace (and not attached):
[1] compiler_4.5.1 magrittr_2.0.3 Rcpp_1.1.0

[jeroen]

Perhaps you are running out of memory. Try adding a image_destroy(eachPdf) at the end of your loop to clear images immediately after writing them (images are automatically destroyed by the gc, but this only runs occasionally).

Could you also test if the same thing happens when using pdftools::pdf_convert()