Switch from Imagemagick to Graphicsmagick.

Note that GM doesn't support gradient:angle so we
have to use a direction. It's radial, not linear,
but is completely acceptable.

Imagemagick silently introduces artifacts and fails
to composite images when the underlying gradient is
of the form { #AAAAAA --> #BBBBBB }, where R=G=B.

Note that { #AAAAAA --> #BBBBBC } works fine. This
is a real bug but isn't a wallpapers problem.

Add a 'prepare-docker' wrapper script, which simply
builds the tarball using a known Graphicsmagick and
not whichever happens to be on the generating system.

1 files changed, 8 insertions, 0 deletions

diff --git a/prepare-docker b/prepare-docker
new file mode 100755
index 0000000..4bf519f
--- /dev/null
+++ b/prepare-docker
@@ -0,0 +1,8 @@
+#!/bin/sh -e
+
+docker run -e UIDGID=$(id -u):$(id -g) -v"$(dirname $(readlink -f "${0}"))":/x -w/x --rm -i alpine:3.18 <<'EOF'
+apk add curl git graphicsmagick xz;
+git config --global --add safe.directory /x;
+/x/prepare;
+chown "${UIDGID}" $(find . -mindepth 1 -maxdepth 1 -type f -name 'adelie-wallpapers-*.tar.xz');
+EOF