Populate single band

Tests/test_file_iptc.py

@@ -2,6 +2,8 @@ from __future__ import annotations
 
 from io import BytesIO
 
+import pytest
+
 from PIL import Image, IptcImagePlugin, TiffImagePlugin, TiffTags
 
 from .helper import assert_image_equal, hopper
@@ -9,21 +11,78 @@ from .helper import assert_image_equal, hopper
 TEST_FILE = "Tests/images/iptc.jpg"
 
 
+def create_iptc_image(info: dict[str, int] = {}) -> BytesIO:
+    def field(tag, value):
+        return bytes((0x1C,) + tag + (0, len(value))) + value
+
+    data = field((3, 60), bytes((info.get("layers", 1), info.get("component", 0))))
+    data += field((3, 120), bytes((info.get("compression", 1),)))
+    if "band" in info:
+        data += field((3, 65), bytes((info["band"] + 1,)))
+    data += field((3, 20), b"\x01")  # width
+    data += field((3, 30), b"\x01")  # height
+    data += field(
+        (8, 10),
+        bytes((info.get("data", 0),)),
+    )
+
+    return BytesIO(data)
+
+
 def test_open() -> None:
     expected = Image.new("L", (1, 1))
 
-    f = BytesIO(
+    f = create_iptc_image()
-        b"\x1c\x03<\x00\x02\x01\x00\x1c\x03x\x00\x01\x01\x1c\x03\x14\x00\x01\x01"
-        b"\x1c\x03\x1e\x00\x01\x01\x1c\x08\n\x00\x01\x00"
-    )
     with Image.open(f) as im:
-        assert im.tile == [("iptc", (0, 0, 1, 1), 25, "raw")]
+        assert im.tile == [("iptc", (0, 0, 1, 1), 25, ("raw", None))]
         assert_image_equal(im, expected)
 
     with Image.open(f) as im:
         assert im.load() is not None
 
 
+def test_field_length() -> None:
+    f = create_iptc_image()
+    f.seek(28)
+    f.write(b"\xff")
+    with pytest.raises(OSError, match="illegal field length in IPTC/NAA file"):
+        with Image.open(f):
+            pass
+
+
+@pytest.mark.parametrize("layers, mode", ((3, "RGB"), (4, "CMYK")))
+def test_layers(layers: int, mode: str) -> None:
+    for band in range(-1, layers):
+        info = {"layers": layers, "component": 1, "data": 5}
+        if band != -1:
+            info["band"] = band
+        f = create_iptc_image(info)
+        with Image.open(f) as im:
+            assert im.mode == mode
+
+            data = [0] * layers
+            data[max(band, 0)] = 5
+            assert im.getpixel((0, 0)) == tuple(data)
+
+
+def test_unknown_compression() -> None:
+    f = create_iptc_image({"compression": 2})
+    with pytest.raises(OSError, match="Unknown IPTC image compression"):
+        with Image.open(f):
+            pass
+
+
+def test_getiptcinfo() -> None:
+    f = create_iptc_image()
+    with Image.open(f) as im:
+        assert IptcImagePlugin.getiptcinfo(im) == {
+            (3, 60): b"\x01\x00",
+            (3, 120): b"\x01",
+            (3, 20): b"\x01",
+            (3, 30): b"\x01",
+        }
+
+
 def test_getiptcinfo_jpg_none() -> None:
     # Arrange
     with hopper() as im:

src/PIL/IptcImagePlugin.py

@@ -96,16 +96,18 @@ class IptcImageFile(ImageFile.ImageFile):
         # mode
         layers = self.info[(3, 60)][0]
         component = self.info[(3, 60)][1]
-        if (3, 65) in self.info:
-            id = self.info[(3, 65)][0] - 1
-        else:
-            id = 0
         if layers == 1 and not component:
             self._mode = "L"
-        elif layers == 3 and component:
+            band = None
-            self._mode = "RGB"[id]
+        else:
+            if layers == 3 and component:
+                self._mode = "RGB"
             elif layers == 4 and component:
-            self._mode = "CMYK"[id]
+                self._mode = "CMYK"
+            if (3, 65) in self.info:
+                band = self.info[(3, 65)][0] - 1
+            else:
+                band = 0
 
         # size
         self._size = self.getint((3, 20)), self.getint((3, 30))
@@ -120,14 +122,16 @@ class IptcImageFile(ImageFile.ImageFile):
         # tile
         if tag == (8, 10):
             self.tile = [
-                ImageFile._Tile("iptc", (0, 0) + self.size, offset, compression)
+                ImageFile._Tile("iptc", (0, 0) + self.size, offset, (compression, band))
             ]
 
     def load(self) -> Image.core.PixelAccess | None:
         if self.tile:
-            offset, compression = self.tile[0][2:]
+            args = self.tile[0].args
+            assert isinstance(args, tuple)
+            compression, band = args
 
-            self.fp.seek(offset)
+            self.fp.seek(self.tile[0].offset)
 
             # Copy image data to temporary file
             o = BytesIO()
@@ -147,6 +151,11 @@ class IptcImageFile(ImageFile.ImageFile):
                     size -= len(s)
 
             with Image.open(o) as _im:
+                if band is not None:
+                    bands = [Image.new("L", _im.size)] * Image.getmodebands(self.mode)
+                    bands[band] = _im
+                    _im = Image.merge(self.mode, bands)
+                else:
                     _im.load()
                 self.im = _im.im
             self.tile = []