From 8b0252f987842bb6d327c4077bf9e75905d87c86 Mon Sep 17 00:00:00 2001
From: relikd <info@relikd.de>
Date: Sat, 28 Feb 2026 22:28:06 +0100
Subject: [PATCH] fix: jp2 image size bytes header

---
 icnsutil/RawData.py      |  35 +++++++++++++++++++++++++++--------
 tests/fixtures/32x32.jpf | Bin 0 -> 2009 bytes
 tests/test_cli.py        |   1 +
 tests/test_icnsutil.py   |   1 +
 4 files changed, 29 insertions(+), 8 deletions(-)
 create mode 100644 tests/fixtures/32x32.jpf

diff --git a/icnsutil/RawData.py b/icnsutil/RawData.py
index 0f42ccc..7d31404 100644
--- a/icnsutil/RawData.py
+++ b/icnsutil/RawData.py
@@ -29,6 +29,32 @@ def determine_file_ext(data: bytes) -> Optional[str]:
     return None
 
 
+def _determine_jp2_size(data: bytes) -> Optional[Tuple[int, int]]:
+    ''' Read raw bytes and extract JPEG2000 image size. '''
+    if data[:4] == b'\xFF\x4F\xFF\x51':
+        w, h = struct.unpack('>II', data[8:16])
+        return w, h
+
+    # fixed "jP" file header 0000000C 6A502020 0D0A870A
+    off = 12
+    filesize = len(data)
+
+    while off < filesize:
+        box_size, box_type = struct.unpack('>I4s', data[off:off+8])
+        # find JP2 Header box
+        if box_type == b'jp2h':
+            child = off + 8  # skip parent header
+            while child < (off + box_size):
+                # find Image Header box
+                if data[child+4:child+8] == b'ihdr':
+                    h, w = struct.unpack('>II', data[child+8:child+16])
+                    return w, h
+
+                child += struct.unpack('>I', data[child:child+4])[0]
+        off += box_size
+    return None
+
+
 def determine_image_size(data: bytes, ext: Optional[str] = None) \
         -> Optional[Tuple[int, int]]:
     ''' Supports PNG, ARGB, and Jpeg 2000 image data. '''
@@ -45,14 +71,7 @@ def determine_image_size(data: bytes, ext: Optional[str] = None) \
             data = data[4:]  # without it32 header
         return IcnsType.match_maxsize(PackBytes.get_size(data), 'rgb').size
     elif ext == 'jp2':
-        if data[:4] == b'\xFF\x4F\xFF\x51':
-            w, h = struct.unpack('>II', data[8:16])
-            return w, h
-        len_ftype = struct.unpack('>I', data[12:16])[0]
-        # file header + type box + header box (super box) + image header box
-        offset = 12 + len_ftype + 8 + 8
-        h, w = struct.unpack('>II', data[offset:offset + 8])
-        return w, h
+        return _determine_jp2_size(data)
     return None  # icns does not support other image types except binary
 
 
diff --git a/tests/fixtures/32x32.jpf b/tests/fixtures/32x32.jpf
new file mode 100644
index 0000000000000000000000000000000000000000..6d25a0e63c88f5d42fe9508713c6900f0b4ef31e
GIT binary patch
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diff --git a/tests/test_cli.py b/tests/test_cli.py
index da7ae0b..b579ff3 100644
--- a/tests/test_cli.py
+++ b/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')
diff --git a/tests/test_icnsutil.py b/tests/test_icnsutil.py
index 5dd0a0a..b09fce3 100644
--- a/tests/test_icnsutil.py
+++ b/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 (