add main.sh & fix packages

Dockerfile

@@ -1,5 +1,7 @@
 FROM docker.io/alpine:latest
-RUN apk add --no-cache imagemagick font-fira-mono-nerd pango imagemagick-pango
+RUN apk add --no-cache imagemagick imagemagick-jpeg imagemagick-pango font-fira-code-nerd
 RUN magick --version
 RUN fc-cache -fv
 RUN fc-list
+COPY ./main.sh /app
+ENTRYPOINT [ "/app/main.sh" ]

main.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env sh
+set -e
+export LC_ALL='C.UTF8'
+
+help_text() {
+  printf "
+-t path to pango formated text file
+   how to format: https://usage.imagemagick.org/text/#pango
+   or as an environment variable IMAGE_TEXT not with path but the text itself
+   if -t is set the environment variable will be ignored
+
+-p is a path to write the file to. Format is determined by file ending.
+   or as an environment variable PICTURE_PATH
+   if -p is set the environment variable will be ignored
+  "
+  exit 1
+}
+
+# directory of the script itself
+SCRIPT_DIR="$(cd -P -- "$(dirname -- "$(command -v -- "$0")")" && pwd -P)"
+export SCRIPT_DIR
+
+# set defaults
+P_PATH="$SCRIPT_DIR/example.jpg"
+I_TEXT="$(cat "$SCRIPT_DIR"/text.pango.example 2>/dev/null || echo 'example text')"
+
+# read from environment variables
+P_PATH="${PICTURE_PATH:-$P_PATH}"
+I_TEXT="${IMAGE_TEXT:-$I_TEXT}"
+
+# options, they override environment variables
+while getopts "p:t:" opt
+do
+  case "$opt" in
+    p) P_PATH="$OPTARG";;
+    t) I_TEXT=$(cat "$OPTARG");;
+    *) help_text
+  esac
+done
+
+magick \
+  -background '#FFFFFF' \
+  -fill '#000000' \
+  -font 'FiraCode Nerd Font' \
+  -pointsize 72 pango:"$I_TEXT" \
+  "$P_PATH"
+