fix padded pbm binary loading

Author: carlossless

adafruit_imageload/pnm/pbm_binary.py

@@ -38,16 +38,18 @@ def load(
     """
     Load a P4 'PBM' binary image into the Bitmap
     """
+    padded_width = (width + 7) // 8 * 8
     x = 0
     y = 0
     while True:
         next_byte = file.read(1)
         if not next_byte:
             break  # out of bits
         for bit in iterbits(next_byte):
-            bitmap[x, y] = bit
+            if x < width:
+                bitmap[x, y] = bit
             x += 1
-            if x > width - 1:
+            if x > padded_width - 1:
                 y += 1
                 x = 0
             if y > height - 1:

examples/images/netpbm_p4_mono_width.pbm

@@ -0,0 +1,3 @@
+P4
+14 20
+�̷���������������{x|��g�C��{x�����

examples/images/netpbm_p4_mono_width.pbm.license

@@ -0,0 +1,2 @@
+# SPDX-FileCopyrightText: 2025 Karolis Stasaitis
+# SPDX-License-Identifier: MIT

tests/test_pbm_load.py

@@ -72,7 +72,7 @@ def test_load_works_p1_ascii(self):
         palette.validate()
 
     def test_load_works_p4_in_mem(self):
-        file = BytesIO(b"P4\n4 2\n\x55")
+        file = BytesIO(b"P4\n4 2\n\x5f\x5f")
         bitmap, palette = pnm.load(
             file, b"P4", bitmap=Bitmap_C_Interface, palette=Palette_C_Interface
         )
@@ -103,6 +103,27 @@ def test_load_works_p4_binary(self):
         self.assertEqual(15, bitmap.height)
         bitmap.validate()
 
+    def test_load_works_p4_binary_padded_width(self):
+        test_file = os.path.join(
+            os.path.dirname(__file__),
+            "..",
+            "examples",
+            "images",
+            "netpbm_p4_mono_width.pbm",
+        )
+        with open(test_file, "rb") as file:
+            bitmap, palette = pnm.load(
+                file, b"P4", bitmap=Bitmap_C_Interface, palette=Palette_C_Interface
+            )
+        self.assertEqual(1, palette.num_colors)
+        palette.validate()
+        self.assertEqual(b"\xff\xff\xff", palette[0])
+        self.assertTrue(isinstance(bitmap, Bitmap_C_Interface))
+        self.assertEqual(1, bitmap.colors)
+        self.assertEqual(14, bitmap.width)
+        self.assertEqual(20, bitmap.height)
+        bitmap.validate()
+
     def test_load_works_p4_binary_high_res(self):
         test_file = os.path.join(
             os.path.dirname(__file__),