diff --git a/ci/ci_shellify.sh b/ci/ci_shellify.sh
new file mode 100755
index 000000000..bf6dd7ce6
--- /dev/null
+++ b/ci/ci_shellify.sh
@@ -0,0 +1,92 @@
+#!/usr/bin/env bash
+set -o errexit -o pipefail -o posix
+
+# Copyright (c) 2019-2024 Cosmin Truta.
+#
+# Use, modification and distribution are subject to the MIT License.
+# Please see the accompanying file LICENSE_MIT.txt
+#
+# SPDX-License-Identifier: MIT
+
+# shellcheck source="ci/lib/ci.lib.sh"
+source "$(dirname "$0")/lib/ci.lib.sh"
+cd "$CI_TOPLEVEL_DIR"
+
+function ci_shellify_c {
+    # Convert C preprocessor text, specifically originating
+    # from png.h, to shell scripting text.
+    # Select only the easy-to-parse definitions of PNG_LIBPNG_*.
+    sed -n -e '/^\# *define * PNG_LIBPNG_[^ ]* * ["0-9A-Za-z_]/ p' |
+        sed -e 's/^\# *define * PNG\([^ ]*\) * \([^ ]*\)/PNG\1=\2/' \
+            -e 's/=PNG\([0-9A-Za-z_]*\)/=\${PNG\1}/' \
+            -e 's/^\([^ ]*=[^ ]*\).*$/export \1;/'
+}
+
+function ci_shellify_autoconf {
+    # Convert autoconf (M4) text, specifically originating
+    # from configure.ac, to shell scripting text.
+    # Select only the easy-to-parse definitions of PNGLIB_*.
+    sed -n -e '/^ *PNGLIB_[^ ]*=[$"0-9A-Za-z_]/ p' |
+        sed -e 's/^ *PNG\([0-9A-Za-z_]*\)=\([^# ]*\).*$/PNG\1=\2/' \
+            -e 's/^\([^ ]*=[^ ]*\).*$/export \1;/'
+}
+
+function ci_shellify_cmake {
+    # Convert CMake lists text, specifically originating
+    # from CMakeLists.txt, to shell scripting text.
+    # Select only the easy-to-parse definitions of PNGLIB_*.
+    sed -n -e '/^ *set *(PNGLIB_[^ ]* * [$"0-9A-Za-z_].*)/ p' |
+        sed -e 's/^ *set *(PNG\([^ ]*\) * \([^() ]*\)).*$/PNG\1=\2/' \
+            -e 's/^\([^ ]*=[^ ]*\).*$/export \1;/'
+}
+
+function ci_shellify {
+    local arg filename
+    for arg in "$@"
+    do
+        test -f "$arg" || ci_err "no such file: '$arg'"
+        filename="$(basename -- "$arg")"
+        case "$filename" in
+        ( *.[ch] )
+            [[ $filename == png.h ]] || {
+                ci_err "unable to shellify: '$filename' (expecting: 'png.h')"
+            }
+            ci_shellify_c <"$arg" ;;
+        ( config* | *.ac )
+            [[ $filename == configure.ac ]] || {
+                ci_err "unable to shellify: '$filename' (expecting: 'configure.ac')"
+            }
+            ci_shellify_autoconf <"$arg" ;;
+        ( *CMake* | *cmake* | *.txt )
+            [[ $filename == [Cc][Mm]ake[Ll]ists.txt ]] || {
+                ci_err "unable to shellify: '$filename' (expecting: 'CMakeLists.txt')"
+            }
+            ci_shellify_cmake <"$arg" ;;
+        ( * )
+            ci_err "unable to shellify: '$arg'" ;;
+        esac
+    done
+}
+
+function usage {
+    echo "usage: $CI_SCRIPT_NAME [<options>] <files>..."
+    echo "options: -?|-h|--help"
+    echo "files: png.h|configure.ac|CMakeLists.txt"
+    exit "${@:-0}"
+}
+
+function main {
+    local opt
+    while getopts ":" opt
+    do
+        # This ain't a while-loop. It only pretends to be.
+        [[ $1 == -[?h]* || $1 == --help || $1 == --help=* ]] && usage 0
+        ci_err "unknown option: '$1'"
+    done
+    shift $((OPTIND - 1))
+    [[ $# -eq 0 ]] && usage 2
+    # And... go!
+    ci_shellify "$@"
+}
+
+main "$@"