Fixed reading 9 to 15-bit PGM

Tests/test_file_ppm.py

@@ -20,6 +20,18 @@ def test_sanity():
         assert im.get_format_mimetype() == "image/x-portable-pixmap"
 
 
+@pytest.mark.parametrize("depth", range(9, 16))
+def test_less_than_16bit_pgm(depth):
+    name = "Tests/images/ppm/" + str(depth) + "_bit"
+    with Image.open(name + ".pgm") as im:
+        im.load()
+        assert im.mode == "I"
+        assert im.size == (128, 128)
+        assert im.get_format_mimetype() == "image/x-portable-graymap"
+
+        assert_image_equal_tofile(im, name + ".png")
+
+
 def test_16bit_pgm():
     with Image.open("Tests/images/16_bit_binary.pgm") as im:
         im.load()

src/PIL/PpmImagePlugin.py

@@ -113,14 +113,15 @@ def _open(self):
             elif ix == 2:  # token is maxval
                 maxval = token
                 if maxval > 255:
-                    if not mode == "L":
+                    if mode != "L":
                         raise ValueError(f"Too many colors for band: {token}")
-                    if maxval < 2**16:
-                        self.mode = "I"
-                        rawmode = "I;16B"
+                    self.mode = "I"
+                    for bit in range(9, 16):
+                        if maxval == 2**bit - 1:
+                            break
                     else:
-                        self.mode = "I"
-                        rawmode = "I;32B"
+                        bit = 16 if maxval < 2**16 else 32
+                    rawmode = "I;" + str(bit) + "B"
 
         self._size = xsize, ysize
         self.tile = [("raw", (0, 0, xsize, ysize), self.fp.tell(), (rawmode, 0, 1))]

src/libImaging/Unpack.c

@@ -1182,6 +1182,40 @@ unpackI12_I16(UINT8 *out, const UINT8 *in, int pixels) {
     }
 }
 
+#ifdef WORDS_BIGENDIAN
+#define UNPACK_IXB(NAME, DEPTH)                                 \
+    static void NAME(UINT8 *out, const UINT8 *in, int pixels) { \
+        int i, pixel;                                           \
+        for (i = 0; i < pixels; i++) {                          \
+            pixel = ((in[0] << 8) + in[1]) << (16 - DEPTH);     \
+            out[2] = pixel >> 8;                                \
+            out[3] = pixel;                                     \
+            in += 2;                                            \
+            out += 4;                                           \
+        }                                                       \
+    }
+#else
+#define UNPACK_IXB(NAME, DEPTH)                                 \
+    static void NAME(UINT8 *out, const UINT8 *in, int pixels) { \
+        int i, pixel;                                           \
+        for (i = 0; i < pixels; i++) {                          \
+            pixel = ((in[0] << 8) + in[1]) << (16 - DEPTH);     \
+            out[0] = pixel;                                     \
+            out[1] = pixel >> 8;                                \
+            in += 2;                                            \
+            out += 4;                                           \
+        }                                                       \
+    }
+#endif
+
+UNPACK_IXB(unpackI9B, 9)
+UNPACK_IXB(unpackI10B, 10)
+UNPACK_IXB(unpackI11B, 11)
+UNPACK_IXB(unpackI12B, 12)
+UNPACK_IXB(unpackI13B, 13)
+UNPACK_IXB(unpackI14B, 14)
+UNPACK_IXB(unpackI15B, 15)
+
 static void
 copy1(UINT8 *out, const UINT8 *in, int pixels) {
     /* L, P */
@@ -1684,6 +1718,13 @@ static struct {
     {"I", "I", 32, copy4},
     {"I", "I;8", 8, unpackI8},
     {"I", "I;8S", 8, unpackI8S},
+    {"I", "I;9B", 16, unpackI9B},
+    {"I", "I;10B", 16, unpackI10B},
+    {"I", "I;11B", 16, unpackI11B},
+    {"I", "I;12B", 16, unpackI12B},
+    {"I", "I;13B", 16, unpackI13B},
+    {"I", "I;14B", 16, unpackI14B},
+    {"I", "I;15B", 16, unpackI15B},
     {"I", "I;16", 16, unpackI16},
     {"I", "I;16S", 16, unpackI16S},
     {"I", "I;16B", 16, unpackI16B},