Deprecate P;2L and P;4L in frombytes()

Tests/test_file_pcx.py

@@ -213,5 +213,6 @@ def test_break_padding(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
 )
 def test_truncated(data_len: int, rawmode: str) -> None:
     data = b"\x00" * data_len
-    with pytest.raises(ValueError, match="not enough image data"):
-        Image.frombuffer("P", (9, 1), data, "raw", rawmode, 0, 1)
+    with pytest.warns(DeprecationWarning, match=rawmode):
+        with pytest.raises(ValueError, match="not enough image data"):
+            Image.frombuffer("P", (9, 1), data, "raw", rawmode, 0, 1)

docs/deprecations.rst

@@ -83,6 +83,15 @@ Image getdata()
 identical, except that it returns a tuple of pixel values, instead of an internal
 Pillow data type.
 
+Reading "P;2L" and "P;4L" raw mode data directly
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. deprecated:: 12.3.0
+
+Using :py:func:`.Image.frombuffer()`, :py:func:`.Image.frombytes()` or
+:py:meth:`~PIL.Image.Image.frombytes()` to read "P;2L" or "P;4L" raw mode data has been
+deprecated.
+
 Removed features
 ----------------
 

docs/releasenotes/12.3.0.rst

@@ -25,10 +25,12 @@ TODO
 Deprecations
 ============
 
-TODO
-^^^^
+Reading "P;2L" and "P;4L" raw mode data directly
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-TODO
+Using :py:func:`.Image.frombuffer()`, :py:func:`.Image.frombytes()` or
+:py:meth:`~PIL.Image.Image.frombytes()` to read "P;2L" or "P;4L" raw mode data has been
+deprecated.
 
 API changes
 ===========

src/PIL/Image.py

@@ -943,11 +943,14 @@ def frombytes(
             # may pass tuple instead of argument list
             decoder_args = decoder_args[0]
 
-        if decoder_args and decoder_args[0] in {"P;2L", "P;4L"}:
-            multiple = 4 if decoder_args[0] == "P;2L" else 8
-            if len(data) % multiple:
-                msg = "not enough image data"
-                raise ValueError(msg)
+        if decoder_args:
+            raw_mode = decoder_args[0]
+            if raw_mode in {"P;2L", "P;4L"}:
+                deprecate(raw_mode, 14)
+                multiple = 4 if raw_mode == "P;2L" else 8
+                if len(data) % multiple:
+                    msg = "not enough image data"
+                    raise ValueError(msg)
 
         # default format
         if decoder_name == "raw" and decoder_args == ():

src/decode.c

@@ -37,6 +37,7 @@
 #include "libImaging/Bit.h"
 #include "libImaging/Bcn.h"
 #include "libImaging/Gif.h"
+#include "libImaging/PcxDecode.h"
 #include "libImaging/Raw.h"
 #include "libImaging/Sgi.h"
 
@@ -618,7 +619,13 @@ PyImaging_PcxDecoderNew(PyObject *self, PyObject *args) {
         return NULL;
     }
 
-    if (get_unpacker(decoder, mode, rawmode) < 0) {
+    if (strcmp(rawmode_name, "P;2L") == 0) {
+        decoder->state.shuffle = unpackP2L;
+        decoder->state.bits = 2;
+    } else if (strcmp(rawmode_name, "P;4L") == 0) {
+        decoder->state.shuffle = unpackP4L;
+        decoder->state.bits = 4;
+    } else if (get_unpacker(decoder, mode, rawmode) < 0) {
         return NULL;
     }
 

src/libImaging/PcxDecode.c

@@ -15,6 +15,37 @@
 
 #include "Imaging.h"
 
+void
+unpackP2L(UINT8 *out, const UINT8 *in, int pixels) {
+    int i, j, m, s;
+    /* bit layers */
+    m = 128;
+    s = (pixels + 7) / 8;
+    for (i = j = 0; i < pixels; i++) {
+        out[i] = ((in[j] & m) ? 1 : 0) + ((in[j + s] & m) ? 2 : 0);
+        if ((m >>= 1) == 0) {
+            m = 128;
+            j++;
+        }
+    }
+}
+
+void
+unpackP4L(UINT8 *out, const UINT8 *in, int pixels) {
+    int i, j, m, s;
+    /* bit layers (trust the optimizer ;-) */
+    m = 128;
+    s = (pixels + 7) / 8;
+    for (i = j = 0; i < pixels; i++) {
+        out[i] = ((in[j] & m) ? 1 : 0) + ((in[j + s] & m) ? 2 : 0) +
+                 ((in[j + 2 * s] & m) ? 4 : 0) + ((in[j + 3 * s] & m) ? 8 : 0);
+        if ((m >>= 1) == 0) {
+            m = 128;
+            j++;
+        }
+    }
+}
+
 int
 ImagingPcxDecode(Imaging im, ImagingCodecState state, UINT8 *buf, Py_ssize_t bytes) {
     UINT8 n;

src/libImaging/PcxDecode.h

@@ -0,0 +1,12 @@
+/*
+ * The Python Imaging Library.
+ * $Id$
+ *
+ * Declarations for PCX decoder.
+ */
+
+extern void
+unpackP2L(UINT8 *out, const UINT8 *in, int pixels);
+
+extern void
+unpackP4L(UINT8 *out, const UINT8 *in, int pixels);

src/libImaging/Unpack.c

@@ -32,6 +32,7 @@
 
 #include "Imaging.h"
 #include "Convert.h"
+#include "PcxDecode.h"
 
 #define R 0
 #define G 1
@@ -548,37 +549,6 @@ unpackP4(UINT8 *out, const UINT8 *in, int pixels) {
     }
 }
 
-static void
-unpackP2L(UINT8 *out, const UINT8 *in, int pixels) {
-    int i, j, m, s;
-    /* bit layers */
-    m = 128;
-    s = (pixels + 7) / 8;
-    for (i = j = 0; i < pixels; i++) {
-        out[i] = ((in[j] & m) ? 1 : 0) + ((in[j + s] & m) ? 2 : 0);
-        if ((m >>= 1) == 0) {
-            m = 128;
-            j++;
-        }
-    }
-}
-
-static void
-unpackP4L(UINT8 *out, const UINT8 *in, int pixels) {
-    int i, j, m, s;
-    /* bit layers (trust the optimizer ;-) */
-    m = 128;
-    s = (pixels + 7) / 8;
-    for (i = j = 0; i < pixels; i++) {
-        out[i] = ((in[j] & m) ? 1 : 0) + ((in[j + s] & m) ? 2 : 0) +
-                 ((in[j + 2 * s] & m) ? 4 : 0) + ((in[j + 3 * s] & m) ? 8 : 0);
-        if ((m >>= 1) == 0) {
-            m = 128;
-            j++;
-        }
-    }
-}
-
 /* Unpack to "RGB" image */
 
 void