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ImageMagick recipes I should stuff into config files or scripts, but
haven't yet.
* Configuration
** Allow conversion from/to PDF
- Open ImageMagick's =policy.xml= configuration file.
- Locate the =<policy>= tag with a =pattern= including "PDF".
- Comment it out.
* Comparing images
~magick compare~ is a thing; ~magick convert~ can also do [[https://stackoverflow.com/a/33673440][neat stuff]]:
#+begin_src sh
convert '(' a.png -flatten -grayscale Rec709Luminance ')' \
'(' b.png -flatten -grayscale Rec709Luminance ')' \
'(' -clone 0-1 -compose darken -composite ')' \
-channel RGB -combine diff.png
#+end_src
* Adding watermarks
Someday, in the Glorious Future, every thirdparty that insists on
having a copy of my personal documents will be legally obligated to
request it from a trusted government service that steganographizes the
requester's identity in the files they send.
Until then…
#+begin_src sh
#!/bin/bash
set -eu
src=$1
dst=$2
label=$3
mark ()
{
local marksrc=$1
local markdst=$2
w=$(identify -format '%w\n' "$marksrc" | head -1)
h=$(identify -format '%h\n' "$marksrc" | head -1)
textw=$((w/3))
texth=$((h/8))
pointsize=$((80*w/2500))
offx=$((100*w/2500))
offy=$((400*h/3500))
convert -size ${textw}x${texth} xc:none \
-fill '#80808080' -pointsize $pointsize \
-annotate 340x340+${offx}+${offy} "$label" \
miff:- | \
composite -tile - "$marksrc" "$markdst"
}
if [[ "$src" =~ \.pdf ]]
then
# AFAICT if I feed a multi-page PDF to composite, it outputs only
# the first page. Jump through hoops to split and concatenate the
# PDF; also, roundtrip through JPG because setting -density (to
# preserve a good quality) messes with the size calculations for
# the label.
tmpd=$(mktemp -d)
bname=$(basename "$src")
qpdf --split-pages "$src" "${tmpd}/$bname"
shopt -s extglob
for page in ${tmpd}/${bname/%.pdf/-+([0-9]).pdf}
do
convert -density 300 -flatten "$page" "${page/.pdf/.jpg}"
mark "${page/.pdf/.jpg}" "${page/.pdf/-MARKED.jpg}"
convert -density 300 "${page/.pdf/-MARKED.jpg}" "${page/.pdf/-MARKED.pdf}"
done
qpdf --empty --pages ${tmpd}/${bname/%.pdf/-+([0-9])-MARKED.pdf} -- "$dst"
exit
fi
mark "$src" "$dst"
#+end_src
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