fix: jp2 image size bytes header

tests/test_cli.py

@@ -146,6 +146,7 @@ class TestCLI_compose(unittest.TestCase):
     def test_jp2(self):
         self.assert_conv_file('256x256.jp2', 'ic08')
         self.assert_conv_file('18x18.j2k', 'icsb', arg=['-f'])
+        self.assert_conv_file('32x32.jpf', 'icp5', arg=['-f'])
 
     def test_argb(self):
         self.assert_conv_file('rgb.icns.argb', 'ic04')

tests/test_icnsutil.py

@@ -444,6 +444,7 @@ class TestRawData(unittest.TestCase):
         self.assertEqual(fn('rgb.icns.argb'), (16, 16))
         self.assertEqual(fn('256x256.jp2'), (256, 256))
         self.assertEqual(fn('18x18.j2k'), (18, 18))
+        self.assertEqual(fn('32x32.jpf'), (32, 32))
 
     def test_ext(self):
         for data, ext in (