Update readme and add package installation

README.md

@@ -1 +1,15 @@
 ## earth_wallpaper
+
+### Description
+
+Obtain an image of the planet earth centered over a city, with the night shadow according to the current time and overlay information about temperature and time.
+
+
+### Requirements
+
+Tested with XFCE4 and Gnome 2. Problems with Gnome >3.
+### Usage
+
+```bash
+earth_wallpaper.sh Tampere
+```

earth_wallpaper.sh

@@ -120,7 +120,16 @@ temperature=$("${wget_cmd}" -q -O - "$weather_url" | egrep -o "<temp_c>-?[0-9]*\
 text="Image from $cur_date at $time\n$city $temperatureº C"
 convert_cmd=$(which convert)
 if [ ! -x "${convert_cmd}" ]; then
-  apt install imagemagick
+  if [ "$(which apt)" != "" ]; then
+    apt install imagemagick
+  elif [ "$(which yum)" != "" ]; then
+    yum install imagemagick
+  elif [ "${which pacman}" != "" ]; then
+    pacman -S imagemagick
+  else
+    message "Install imagemagick using your package manager." p
+    exit 1
+  fi
 fi
 run_and_log "${convert_cmd}" $wallpaper_file -pointsize 50 -font "${font_name}" -fill "#505050" -gravity SouthEast -annotate +0+0 "$text" $wallpaper_file
 error_code=$?