diff --git a/pytmx/pytmx.py b/pytmx/pytmx.py
index 7d40621..9bbe454 100644
--- a/pytmx/pytmx.py
+++ b/pytmx/pytmx.py
@@ -17,6 +17,7 @@
 License along with pytmx.  If not, see <https://www.gnu.org/licenses/>.
 
 """
+
 from __future__ import annotations
 
 import gzip
@@ -54,6 +55,8 @@
     "convert_to_bool",
     "resolve_to_class",
     "parse_properties",
+    "decode_gid",
+    "unpack_gids",
 )
 
 logger = logging.getLogger(__name__)
@@ -85,6 +88,7 @@
 TiledLayer = Union[
     "TiledTileLayer", "TiledImageLayer", "TiledGroupLayer", "TiledObjectGroup"
 ]
+flag_cache: dict[int, TileFlags] = {}
 
 # need a more graceful way to handle annotations for optional dependencies
 if pygame:
@@ -125,15 +129,19 @@ def decode_gid(raw_gid: int) -> tuple[int, TileFlags]:
     """
     if raw_gid < GID_TRANS_ROT:
         return raw_gid, empty_flags
-    return (
-        raw_gid & ~GID_MASK,
-        # TODO: cache all combinations of flags
-        TileFlags(
-            raw_gid & GID_TRANS_FLIPX == GID_TRANS_FLIPX,
-            raw_gid & GID_TRANS_FLIPY == GID_TRANS_FLIPY,
-            raw_gid & GID_TRANS_ROT == GID_TRANS_ROT,
-        ),
+
+    # Check if the GID is already in the cache
+    if raw_gid in flag_cache:
+        return raw_gid & ~GID_MASK, flag_cache[raw_gid]
+
+    # Calculate and cache the flags
+    flags = TileFlags(
+        raw_gid & GID_TRANS_FLIPX == GID_TRANS_FLIPX,
+        raw_gid & GID_TRANS_FLIPY == GID_TRANS_FLIPY,
+        raw_gid & GID_TRANS_ROT == GID_TRANS_ROT,
     )
+    flag_cache[raw_gid] = flags
+    return raw_gid & ~GID_MASK, flags
 
 
 def reshape_data(
diff --git a/tests/pytmx/test_pytmx.py b/tests/pytmx/test_pytmx.py
index 9ab99ef..c8f1211 100644
--- a/tests/pytmx/test_pytmx.py
+++ b/tests/pytmx/test_pytmx.py
@@ -1,7 +1,24 @@
 import unittest
 
 import pytmx
-from pytmx import TiledElement, convert_to_bool
+import base64
+import gzip
+import zlib
+import struct
+from pytmx import (
+    TiledElement,
+    TiledMap,
+    convert_to_bool,
+    TileFlags,
+    decode_gid,
+    unpack_gids,
+)
+
+# Tiled gid flags
+GID_TRANS_FLIPX = 1 << 31
+GID_TRANS_FLIPY = 1 << 30
+GID_TRANS_ROT = 1 << 29
+GID_MASK = GID_TRANS_FLIPX | GID_TRANS_FLIPY | GID_TRANS_ROT
 
 
 class TestConvertToBool(unittest.TestCase):
@@ -64,6 +81,15 @@ def test_non_boolean_number_raises_error(self) -> None:
         with self.assertRaises(ValueError):
             convert_to_bool("200")
 
+    def test_edge_cases(self):
+        # Whitespace
+        self.assertTrue(convert_to_bool("  t  "))
+        self.assertFalse(convert_to_bool("  f  "))
+
+        # Numeric edge cases
+        self.assertTrue(convert_to_bool(1e-10))  # Very small positive number
+        self.assertFalse(convert_to_bool(-1e-10))  # Very small negative number
+
 
 class TiledMapTest(unittest.TestCase):
     filename = "tests/resources/test01.tmx"
@@ -170,3 +196,145 @@ def test_reserved_names_check_disabled_with_option(self) -> None:
     def test_repr(self) -> None:
         self.element.name = "foo"
         self.assertEqual('<TiledElement: "foo">', self.element.__repr__())
+
+
+class TestDecodeGid(unittest.TestCase):
+    def test_no_flags(self):
+        raw_gid = 100
+        expected_gid, expected_flags = 100, TileFlags(False, False, False)
+        self.assertEqual(decode_gid(raw_gid), (expected_gid, expected_flags))
+
+    def test_individual_flags(self):
+        # Test for each flag individually
+        test_cases = [
+            (GID_TRANS_FLIPX + 1, 1, TileFlags(True, False, False)),
+            (GID_TRANS_FLIPY + 1, 1, TileFlags(False, True, False)),
+            (GID_TRANS_ROT + 1, 1, TileFlags(False, False, True)),
+        ]
+        for raw_gid, expected_gid, expected_flags in test_cases:
+            self.assertEqual(decode_gid(raw_gid), (expected_gid, expected_flags))
+
+    def test_combinations_of_flags(self):
+        # Test combinations of flags
+        test_cases = [
+            (GID_TRANS_FLIPX + GID_TRANS_FLIPY + 1, 1, TileFlags(True, True, False)),
+            (GID_TRANS_FLIPX + GID_TRANS_ROT + 1, 1, TileFlags(True, False, True)),
+            (GID_TRANS_FLIPY + GID_TRANS_ROT + 1, 1, TileFlags(False, True, True)),
+            (
+                GID_TRANS_FLIPX + GID_TRANS_FLIPY + GID_TRANS_ROT + 1,
+                1,
+                TileFlags(True, True, True),
+            ),
+        ]
+        for raw_gid, expected_gid, expected_flags in test_cases:
+            self.assertEqual(decode_gid(raw_gid), (expected_gid, expected_flags))
+
+    def test_edge_cases(self):
+        # Maximum GID
+        # max_gid = 2**32 - 1
+        # self.assertEqual(decode_gid(max_gid), (max_gid & ~GID_MASK, TileFlags(False, False, False)))
+
+        # Minimum GID
+        min_gid = 0
+        self.assertEqual(decode_gid(min_gid), (min_gid, TileFlags(False, False, False)))
+
+        # GID with all flags set
+        gid_all_flags = GID_TRANS_FLIPX + GID_TRANS_FLIPY + GID_TRANS_ROT + 1
+        self.assertEqual(decode_gid(gid_all_flags), (1, TileFlags(True, True, True)))
+
+        # GID with flags in different orders
+        test_cases = [
+            (GID_TRANS_FLIPX + GID_TRANS_FLIPY + 1, 1, TileFlags(True, True, False)),
+            (GID_TRANS_FLIPY + GID_TRANS_FLIPX + 1, 1, TileFlags(True, True, False)),
+            (GID_TRANS_FLIPX + GID_TRANS_ROT + 1, 1, TileFlags(True, False, True)),
+            (GID_TRANS_ROT + GID_TRANS_FLIPX + 1, 1, TileFlags(True, False, True)),
+        ]
+        for raw_gid, expected_gid, expected_flags in test_cases:
+            self.assertEqual(decode_gid(raw_gid), (expected_gid, expected_flags))
+
+
+class TestRegisterGid(unittest.TestCase):
+    def setUp(self):
+        self.tmx_map = TiledMap()
+
+    def test_register_gid_with_valid_tiled_gid(self):
+        gid = self.tmx_map.register_gid(123)
+        self.assertIsNotNone(gid)
+
+    def test_register_gid_with_flags(self):
+        flags = TileFlags(1, 0, 1)
+        gid = self.tmx_map.register_gid(456, flags)
+        self.assertIsNotNone(gid)
+
+    def test_register_gid_zero(self):
+        gid = self.tmx_map.register_gid(0)
+        self.assertEqual(gid, 0)
+
+    def test_register_gid_max_gid(self):
+        max_gid = self.tmx_map.maxgid
+        self.tmx_map.register_gid(max_gid)
+        self.assertEqual(self.tmx_map.maxgid, max_gid + 1)
+
+    def test_register_gid_duplicate_gid(self):
+        gid1 = self.tmx_map.register_gid(123)
+        gid2 = self.tmx_map.register_gid(123)
+        self.assertEqual(gid1, gid2)
+
+    def test_register_gid_duplicate_gid_different_flags(self):
+        gid1 = self.tmx_map.register_gid(123, TileFlags(1, 0, 0))
+        gid2 = self.tmx_map.register_gid(123, TileFlags(0, 1, 0))
+        self.assertNotEqual(gid1, gid2)
+
+    def test_register_gid_empty_flags(self):
+        gid = self.tmx_map.register_gid(123, TileFlags(0, 0, 0))
+        self.assertIsNotNone(gid)
+
+    def test_register_gid_all_flags_set(self):
+        gid = self.tmx_map.register_gid(123, TileFlags(1, 1, 1))
+        self.assertIsNotNone(gid)
+
+    def test_register_gid_repeated_registration(self):
+        gid1 = self.tmx_map.register_gid(123)
+        gid2 = self.tmx_map.register_gid(123)
+        self.assertEqual(gid1, gid2)
+
+
+class TestUnpackGids(unittest.TestCase):
+    def test_base64_no_compression(self):
+        gids = [123, 456, 789]
+        data = struct.pack("<LLL", *gids)
+        text = base64.b64encode(data).decode("utf-8")
+        result = unpack_gids(text, encoding="base64")
+        self.assertEqual(result, gids)
+
+    def test_base64_gzip_compression(self):
+        gids = [123, 456, 789]
+        data = struct.pack("<LLL", *gids)
+        compressed_data = gzip.compress(data)
+        text = base64.b64encode(compressed_data).decode("utf-8")
+        result = unpack_gids(text, encoding="base64", compression="gzip")
+        self.assertEqual(result, gids)
+
+    def test_base64_zlib_compression(self):
+        gids = [123, 456, 789]
+        data = struct.pack("<LLL", *gids)
+        compressed_data = zlib.compress(data)
+        text = base64.b64encode(compressed_data).decode("utf-8")
+        result = unpack_gids(text, encoding="base64", compression="zlib")
+        self.assertEqual(result, gids)
+
+    def test_base64_unsupported_compression(self):
+        text = "some_base64_data"
+        with self.assertRaises(ValueError):
+            unpack_gids(text, encoding="base64", compression="unsupported")
+
+    def test_csv(self):
+        gids = [123, 456, 789]
+        text = ",".join(map(str, gids))
+        result = unpack_gids(text, encoding="csv")
+        self.assertEqual(result, gids)
+
+    def test_unsupported_encoding(self):
+        text = "some_data"
+        with self.assertRaises(ValueError):
+            unpack_gids(text, encoding="unsupported")