Add image filter and update README

hack/image-filter.sh

@@ -0,0 +1,78 @@
+#!/usr/bin/env bash
+
+if [[ "${#}" -ne 0 && "$1" != "-" ]]; then
+    tmp=$(cat "${1}")
+else
+    tmp=$(cat)
+fi
+
+domains=(
+    cr.l5d.io
+    docker.elastic.co
+    docker.io
+    gcr.io
+    ghcr.io
+    k8s.gcr.io
+    mcr.microsoft.com
+    nvcr.io
+    quay.io
+    registry.jujucharms.com
+    rocks.canonical.com
+)
+
+SUFFIX=${SUFFIX:-"m.daocloud.io"}
+
+function replace_domain() {
+    local domain="${1}"
+    IFS='.' read -ra arr <<<"${domain}"
+    local len=${#arr[@]}
+    if [[ "${len}" -eq 2 ]]; then
+        echo "${arr[0]}.${SUFFIX}"
+        return 0
+    fi
+
+    if [[ "${arr[0]}" == "registry" ]]; then
+        echo "${arr[1]}.${SUFFIX}"
+        return 0
+    fi
+    if [[ "${arr[0]}" == "docker" ]]; then
+        echo "${arr[1]}.${SUFFIX}"
+        return 0
+    fi
+    if [[ "${arr[0]}" == "cr" ]]; then
+        echo "${arr[1]}.${SUFFIX}"
+        return 0
+    fi
+
+    if [[ "${arr[0]}" =~ cr$ ]]; then
+        echo "${arr[0]}.${SUFFIX}"
+        return 0
+    fi
+
+    unset 'arr[${#arr[@]}-1]'
+
+    IFS='-'
+    echo "${arr[*]}.${SUFFIX}"
+
+    unset IFS
+    return 0
+}
+
+function replace_all() {
+    tmp="${1}"
+    for line in ${domains[*]}; do
+        key="${line}"
+        val="$(replace_domain ${line})"
+        if [[ "${key}" == "" || "${val}" == "" ]]; then
+            continue
+        fi
+        tmp="$(echo "${tmp}" | sed -e "s# ${key}# ${val}#g")"
+    done
+
+    # Remove sha256 hash
+    tmp="$(echo "${tmp}" | sed -e "s#@sha256:[0-9a-f]\{64\}##g")"
+    echo "${tmp}"
+}
+
+
+replace_all "${tmp}"