diff --git a/scripts/README.txt b/scripts/README.txt
index 3d911ef..49f00db 100644
--- a/scripts/README.txt
+++ b/scripts/README.txt
@@ -75,5 +75,9 @@
  macro.lst         =>  Used by autoconf tools
  prefix.dfn        =>  Used by autoconf tools
 
+ ci_autotools.sh   =>  Continuous integration utility for the Autotools build
+ ci_cmake.sh       =>  Continuous integration utility for the CMake build
+ ci_legacy.sh      =>  Continuous integration utility for the legacy makefiles
 
-Further information can be found in comments in the individual makefiles.
+Further information can be found in comments in the individual scripts and
+makefiles.
diff --git a/scripts/ci_autotools.sh b/scripts/ci_autotools.sh
new file mode 100755
index 0000000..8cc70fe
--- /dev/null
+++ b/scripts/ci_autotools.sh
@@ -0,0 +1,76 @@
+#!/usr/bin/env bash
+set -e
+
+# ci_autotools.sh
+# Continuously integrate libpng using the GNU Autotools.
+#
+# Copyright (c) 2019-2020 Cosmin Truta.
+#
+# This software is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer and license
+# in png.h.
+
+CI_SCRIPTNAME="$(basename "$0")"
+CI_SCRIPTDIR="$(cd "$(dirname "$0")" && pwd)"
+CI_SRCDIR="$(dirname "$CI_SCRIPTDIR")"
+CI_BUILDDIR="$CI_SRCDIR/out/autotools.build"
+
+function ci_info {
+    printf >&2 "%s: %s\\n" "$CI_SCRIPTNAME" "$*"
+}
+
+function ci_err {
+    printf >&2 "%s: error: %s\\n" "$CI_SCRIPTNAME" "$*"
+    exit 2
+}
+
+function ci_spawn {
+    printf >&2 "%s: executing:" "$CI_SCRIPTNAME"
+    printf >&2 " %q" "$@"
+    printf >&2 "\\n"
+    "$@"
+}
+
+function ci_init_autotools {
+    # Initialize the CI_ variables with default values, where applicable.
+    CI_MAKE="${CI_MAKE:-make}"
+    [[ $(uname -s || echo unknown) == Darwin ]] && CI_CC="${CI_CC:-clang}"
+    # Print the CI_ variables.
+    ci_info "source directory: $CI_SRCDIR"
+    ci_info "build directory: $CI_BUILDDIR"
+    ci_info "environment option: \$CI_CONFIGURE_FLAGS='$CI_CONFIGURE_FLAGS'"
+    ci_info "environment option: \$CI_MAKE='$CI_MAKE'"
+    ci_info "environment option: \$CI_MAKE_FLAGS='$CI_MAKE_FLAGS'"
+    ci_info "environment option: \$CI_CC='$CI_CC'"
+    ci_info "environment option: \$CI_CC_FLAGS='$CI_CC_FLAGS'"
+    ci_info "environment option: \$CI_SANITIZERS='$CI_SANITIZERS'"
+    ci_info "environment option: \$CI_NO_TEST='$CI_NO_TEST'"
+    ci_info "environment option: \$CI_NO_CLEAN='$CI_NO_CLEAN'"
+    # Avoid using the CI_ variables that cannot be customized reliably.
+    [[ ! $CI_CONFIGURE_VARS ]] || ci_err "unexpected: \$CI_CONFIGURE_VARS='$CI_CONFIGURE_VARS'"
+    [[ ! $CI_MAKE_VARS ]] || ci_err "unexpected: \$CI_MAKE_VARS='$CI_MAKE_VARS'"
+}
+
+function ci_build_autotools {
+    # Initialize the configure environment.
+    [[ $CI_CC ]] && export CC="$CI_CC"
+    [[ $CI_CC_FLAGS ]] && export CFLAGS="$CI_CC_FLAGS"
+    [[ $CI_SANITIZERS ]] && export CFLAGS="-fsanitize=$CI_SANITIZERS -O2 $CFLAGS"
+    # Build.
+    ci_spawn rm -fr "$CI_BUILDDIR"
+    ci_spawn mkdir -p "$CI_BUILDDIR"
+    ci_spawn cd "$CI_BUILDDIR"
+    ci_spawn "$CI_SRCDIR/configure" $CI_CONFIGURE_FLAGS
+    ci_spawn "$CI_MAKE" $CI_MAKE_FLAGS
+    [[ $CI_NO_TEST ]] || ci_spawn "$CI_MAKE" $CI_MAKE_FLAGS test
+    [[ $CI_NO_CLEAN ]] || ci_spawn "$CI_MAKE" $CI_MAKE_FLAGS clean
+    [[ $CI_NO_CLEAN ]] || ci_spawn "$CI_MAKE" $CI_MAKE_FLAGS distclean
+    ci_info "success!"
+}
+
+ci_init_autotools
+[[ ! $* ]] || {
+    ci_info "note: this program accepts environment options only"
+    ci_err "unexpected command arguments: '$*'"
+}
+ci_build_autotools
diff --git a/scripts/ci_cmake.sh b/scripts/ci_cmake.sh
new file mode 100755
index 0000000..c868ef8
--- /dev/null
+++ b/scripts/ci_cmake.sh
@@ -0,0 +1,95 @@
+#!/usr/bin/env bash
+set -e
+
+# ci_cmake.sh
+# Continuously integrate libpng using CMake.
+#
+# Copyright (c) 2019-2020 Cosmin Truta.
+#
+# This software is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer and license
+# in png.h.
+
+CI_SCRIPTNAME="$(basename "$0")"
+CI_SCRIPTDIR="$(cd "$(dirname "$0")" && pwd)"
+CI_SRCDIR="$(dirname "$CI_SCRIPTDIR")"
+CI_BUILDDIR="$CI_SRCDIR/out/cmake.build"
+
+function ci_info {
+    printf >&2 "%s: %s\\n" "$CI_SCRIPTNAME" "$*"
+}
+
+function ci_err {
+    printf >&2 "%s: error: %s\\n" "$CI_SCRIPTNAME" "$*"
+    exit 2
+}
+
+function ci_spawn {
+    printf >&2 "%s: executing:" "$CI_SCRIPTNAME"
+    printf >&2 " %q" "$@"
+    printf >&2 "\\n"
+    "$@"
+}
+
+function ci_init_cmake {
+    # Initialize the CI_ variables with default values, where applicable.
+    CI_CMAKE="${CI_CMAKE:-cmake}"
+    CI_CTEST="${CI_CTEST:-ctest}"
+    [[ $(uname -s || echo unknown) == Darwin ]] && CI_CC="${CI_CC:-clang}"
+    CI_CMAKE_BUILD_TYPE="${CI_CMAKE_BUILD_TYPE:-Release}"
+    # Print the CI_ variables.
+    ci_info "source directory: $CI_SRCDIR"
+    ci_info "build directory: $CI_BUILDDIR"
+    ci_info "environment option: \$CI_CMAKE='$CI_CMAKE'"
+    ci_info "environment option: \$CI_CMAKE_GENERATOR='$CI_CMAKE_GENERATOR'"
+    ci_info "environment option: \$CI_CMAKE_GENERATOR_PLATFORM='$CI_CMAKE_GENERATOR_PLATFORM'"
+    ci_info "environment option: \$CI_CMAKE_BUILD_TYPE='$CI_CMAKE_BUILD_TYPE'"
+    ci_info "environment option: \$CI_CMAKE_BUILD_FLAGS='$CI_CMAKE_BUILD_FLAGS'"
+    ci_info "environment option: \$CI_CMAKE_VARS='$CI_CMAKE_VARS'"
+    ci_info "environment option: \$CI_CTEST='$CI_CTEST'"
+    ci_info "environment option: \$CI_CTEST_FLAGS='$CI_CTEST_FLAGS'"
+    ci_info "environment option: \$CI_CC='$CI_CC'"
+    ci_info "environment option: \$CI_CC_FLAGS='$CI_CC_FLAGS'"
+    ci_info "environment option: \$CI_SANITIZERS='$CI_SANITIZERS'"
+    ci_info "environment option: \$CI_NO_TEST='$CI_NO_TEST'"
+    ci_info "environment option: \$CI_NO_CLEAN='$CI_NO_CLEAN'"
+}
+
+function ci_build_cmake {
+    # Initialize the CMake environment.
+    [[ $CI_CMAKE_GENERATOR ]] &&
+        export CMAKE_GENERATOR="$CI_CMAKE_GENERATOR"
+    [[ $CI_CMAKE_GENERATOR_PLATFORM ]] &&
+        export CMAKE_GENERATOR_PLATFORM="$CI_CMAKE_GENERATOR_PLATFORM"
+    # Initialize ALL_CC_FLAGS as a string.
+    local ALL_CC_FLAGS="$CI_CC_FLAGS"
+    [[ $CI_SANITIZERS ]] && ALL_CC_FLAGS="-fsanitize=$CI_SANITIZERS $ALL_CC_FLAGS"
+    # Initialize ALL_CMAKE_VARS as an array;
+    # expand CI_CMAKE_VARS at the end of ALL_CMAKE_VARS.
+    local -a ALL_CMAKE_VARS=()
+    [[ $CI_CC ]] && ALL_CMAKE_VARS+=("-DCMAKE_C_COMPILER=$CI_CC")
+    [[ $ALL_CC_FLAGS ]] && ALL_CMAKE_VARS+=("-DCMAKE_C_FLAGS=$ALL_CC_FLAGS")
+    ALL_CMAKE_VARS+=("-DCMAKE_BUILD_TYPE=$CI_CMAKE_BUILD_TYPE")
+    ALL_CMAKE_VARS+=("-DCMAKE_VERBOSE_MAKEFILE=ON")
+    ALL_CMAKE_VARS+=($CI_CMAKE_VARS)
+    # Build.
+    ci_spawn "$(command -v "$CI_CMAKE")" --version
+    ci_spawn "$(command -v "$CI_CTEST")" --version
+    ci_spawn "$CI_CMAKE" -E remove_directory "$CI_BUILDDIR"
+    ci_spawn "$CI_CMAKE" -E make_directory "$CI_BUILDDIR"
+    ci_spawn cd "$CI_BUILDDIR"
+    ci_spawn "$CI_CMAKE" "${ALL_CMAKE_VARS[@]}" "$CI_SRCDIR"
+    ci_spawn "$CI_CMAKE" --build . --config "$CI_CMAKE_BUILD_TYPE" $CI_CMAKE_BUILD_FLAGS
+    [[ $CI_NO_TEST ]] ||
+        ci_spawn "$CI_CTEST" --build-config "$CI_CMAKE_BUILD_TYPE" $CI_CTEST_FLAGS
+    [[ $CI_NO_CLEAN ]] ||
+        ci_spawn "$CI_CMAKE" --build . --config "$CI_CMAKE_BUILD_TYPE" $CI_CMAKE_BUILD_FLAGS --target clean
+    ci_info "success!"
+}
+
+ci_init_cmake
+[[ ! $* ]] || {
+    ci_info "note: this program accepts environment options only"
+    ci_err "unexpected command arguments: '$*'"
+}
+ci_build_cmake
diff --git a/scripts/ci_legacy.sh b/scripts/ci_legacy.sh
new file mode 100755
index 0000000..77f73c9
--- /dev/null
+++ b/scripts/ci_legacy.sh
@@ -0,0 +1,100 @@
+#!/usr/bin/env bash
+set -e
+
+# ci_legacy.sh
+# Continuously integrate libpng using the legacy makefiles.
+#
+# Copyright (c) 2019-2020 Cosmin Truta.
+#
+# This software is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer and license
+# in png.h.
+
+CI_SCRIPTNAME="$(basename "$0")"
+CI_SCRIPTDIR="$(cd "$(dirname "$0")" && pwd)"
+CI_SRCDIR="$(dirname "$CI_SCRIPTDIR")"
+CI_BUILDDIR="$CI_SRCDIR"
+
+function ci_info {
+    printf >&2 "%s: %s\\n" "$CI_SCRIPTNAME" "$*"
+}
+
+function ci_err {
+    printf >&2 "%s: error: %s\\n" "$CI_SCRIPTNAME" "$*"
+    exit 2
+}
+
+function ci_spawn {
+    printf >&2 "%s: executing:" "$CI_SCRIPTNAME"
+    printf >&2 " %q" "$@"
+    printf >&2 "\\n"
+    "$@"
+}
+
+function ci_init_legacy {
+    # Initialize the CI_ variables with default values, where applicable.
+    CI_MAKE="${CI_MAKE:-make}"
+    [[ $(uname -s || echo unknown) == Darwin ]] && CI_CC="${CI_CC:-clang}"
+    [[ $CI_CC == *clang* ]] &&
+        CI_LEGACY_MAKEFILES="${CI_LEGACY_MAKEFILES:-scripts/makefile.clang}"
+    CI_LEGACY_MAKEFILES="${CI_LEGACY_MAKEFILES:-scripts/makefile.gcc}"
+    CI_LD="${CI_LD:-$CI_CC}"
+    CI_LIBS="${CI_LIBS:--lz -lm}"
+    # Print the CI_ variables.
+    ci_info "source directory: $CI_SRCDIR"
+    ci_info "build directory: $CI_BUILDDIR"
+    ci_info "environment option: \$CI_LEGACY_MAKEFILES='$CI_LEGACY_MAKEFILES'"
+    ci_info "environment option: \$CI_MAKE='$CI_MAKE'"
+    ci_info "environment option: \$CI_MAKE_FLAGS='$CI_MAKE_FLAGS'"
+    ci_info "environment option: \$CI_MAKE_VARS='$CI_MAKE_VARS'"
+    ci_info "environment option: \$CI_CC='$CI_CC'"
+    ci_info "environment option: \$CI_CC_FLAGS='$CI_CC_FLAGS'"
+    ci_info "environment option: \$CI_CPP='$CI_CPP'"
+    ci_info "environment option: \$CI_CPP_FLAGS='$CI_CPP_FLAGS'"
+    ci_info "environment option: \$CI_LD='$CI_LD'"
+    ci_info "environment option: \$CI_LD_FLAGS='$CI_LD_FLAGS'"
+    ci_info "environment option: \$CI_LIBS='$CI_LIBS'"
+    ci_info "environment option: \$CI_SANITIZERS='$CI_SANITIZERS'"
+    ci_info "environment option: \$CI_NO_TEST='$CI_NO_TEST'"
+    ci_info "environment option: \$CI_NO_CLEAN='$CI_NO_CLEAN'"
+}
+
+function ci_build_legacy {
+    # Initialize ALL_CC_FLAGS and ALL_LD_FLAGS as strings.
+    local ALL_CC_FLAGS="$CI_CC_FLAGS"
+    local ALL_LD_FLAGS="$CI_LD_FLAGS"
+    [[ $CI_SANITIZERS ]] && {
+        ALL_CC_FLAGS="-fsanitize=$CI_SANITIZERS -O2 $ALL_CC_FLAGS"
+        ALL_LD_FLAGS="-fsanitize=$CI_SANITIZERS $ALL_LD_FLAGS"
+    }
+    # Initialize ALL_MAKE_ARGS as an array;
+    # expand CI_MAKE_FLAGS at the beginning and CI_MAKE_VARS at the end.
+    local -a ALL_MAKE_ARGS=()
+    ALL_MAKE_ARGS+=($CI_MAKE_FLAGS)
+    [[ $CI_CC ]] && ALL_MAKE_ARGS+=("CC=$CI_CC")
+    [[ $ALL_CC_FLAGS ]] && ALL_MAKE_ARGS+=("CFLAGS=$ALL_CC_FLAGS")
+    [[ $CI_CPP ]] && ALL_MAKE_ARGS+=("CPP=$CI_CPP")
+    [[ $CI_CPP_FLAGS ]] && ALL_MAKE_ARGS+=("CPPFLAGS=$CI_CPP_FLAGS")
+    [[ $CI_LD ]] && ALL_MAKE_ARGS+=("LD=$CI_LD")
+    [[ $ALL_LD_FLAGS ]] && ALL_MAKE_ARGS+=("LDFLAGS=$ALL_LD_FLAGS")
+    ALL_MAKE_ARGS+=("LIBS=$CI_LIBS")
+    ALL_MAKE_ARGS+=($CI_MAKE_VARS)
+    # Build.
+    ci_spawn cd "$CI_SRCDIR"
+    [[ $CI_LEGACY_MAKEFILES ]] || ci_err "bad or missing: \$CI_LEGACY_MAKEFILES"
+    local MY_MAKEFILE
+    for MY_MAKEFILE in $CI_LEGACY_MAKEFILES
+    do
+        ci_spawn "$CI_MAKE" "${ALL_MAKE_ARGS[@]}" -f $MY_MAKEFILE
+        [[ $CI_NO_TEST ]] || ci_spawn "$CI_MAKE" "${ALL_MAKE_ARGS[@]}" -f $MY_MAKEFILE test
+        [[ $CI_NO_CLEAN ]] || ci_spawn "$CI_MAKE" "${ALL_MAKE_ARGS[@]}" -f $MY_MAKEFILE clean
+    done
+    ci_info "success!"
+}
+
+ci_init_legacy
+[[ ! $* ]] || {
+    ci_info "note: this program accepts environment options only"
+    ci_err "unexpected command arguments: '$*'"
+}
+ci_build_legacy