I'm trying to convert a PDF to a PNG image (at least the cover of one). I'm successfully extracting the first page of the PDF with pdftk. I'm using imagemagick to do the conversion:
convert cover.pdf cover.png
This works, but unfortunately the cover.png comes through incorrectly rendered (some of the alpha object in the PDF aren't rendered properly). I know ImageMagick uses GhostScript to do the conversion and if I do it directly with gs I can get the desired results, but I'd rather use the convert library as it has other tools I'd like to leverage.
This command in GhostScript accomplishes the desired image:
gs -sDEVICE=pngalpha -sOutputFile=cover.png -r144 cover.pdf
I'm wondering is there any way to pass arguments through convert to GhostScript or am I stuck with calling GhostScript directly?
You can use one commandline with two commands (gs
, convert
) connected through a pipe, if the first command can write its output to stdout, and if the second one can read its input from stdin.
... -o %stdout ...
). convert -background transparent - output.png
).Problem solved:
Complete solution:
gs -sDEVICE=pngalpha \
-o %stdout \
-r144 cover.pdf \
| \
convert \
-background transparent \
- \
cover.png
If you want to have a separate PNG per PDF page, you can use the %d
syntax:
gs -sDEVICE=pngalpha -o file-%03d.png -r144 cover.pdf
This will create PNG files named page-000.png
, page-001.png
, ... (Note that the %d
-counting is zero-based -- file-000.png
corresponds to page 1 of the PDF, 001
to page 2...
Or, if you want to keep your transparent background, for a 100-page PDF, do
for i in {1..100}; do \
\
gs -sDEVICE=pngalpha \
-dFirstPage="${i}" \
-dLastPage="${i}" \
-o %stdout \
-r144 input.pdf \
| \
convert \
-background transparent \
- \
page-${i}.png ; \
\
done