Correctly handle odd sized PCX Images

CHANGES.rst

@@ -4,6 +4,9 @@ Changelog (Pillow)
 2.4.0 (unreleased)
 ------------------
 
+- Fixed opening and saving odd sized .pcx files
+  [wiredfool]
+
 - Fixed saving mode P image as a PNG with transparency = palette color 0
   [d-schmidt]
 

PIL/PcxImagePlugin.py

@@ -55,12 +55,18 @@ def _open(self):
         bbox = i16(s,4), i16(s,6), i16(s,8)+1, i16(s,10)+1
         if bbox[2] <= bbox[0] or bbox[3] <= bbox[1]:
             raise SyntaxError("bad PCX image size")
+        if Image.DEBUG:
+            print ("BBox: %s %s %s %s" % bbox)
+
 
         # format
         version = i8(s[1])
         bits = i8(s[3])
         planes = i8(s[65])
         stride = i16(s,66)
+        if Image.DEBUG:
+            print ("PCX version %s, bits %s, planes %s, stride %s" %
+                   (version, bits, planes, stride))
 
         self.info["dpi"] = i16(s,12), i16(s,14)
 
@@ -98,7 +104,9 @@ def _open(self):
         self.size = bbox[2]-bbox[0], bbox[3]-bbox[1]
 
         bbox = (0, 0) + self.size
-
+        if Image.DEBUG:
+            print ("size: %sx%s" % self.size)
+
         self.tile = [("pcx", bbox, self.fp.tell(), (rawmode, planes * stride))]
 
 # --------------------------------------------------------------------
@@ -126,6 +134,16 @@ def _save(im, fp, filename, check=0):
 
     # bytes per plane
     stride = (im.size[0] * bits + 7) // 8
+    # stride should be even
+    stride = stride + (stride % 2)
+    # Stride needs to be kept in sync with the PcxEncode.c version.
+    # Ideally it should be passed in in the state, but the bytes value
+    # gets overwritten. 
+
+
+    if Image.DEBUG:
+        print ("PcxImagePlugin._save: xwidth: %d, bits: %d, stride: %d" % (
+            im.size[0], bits, stride))
 
     # under windows, we could determine the current screen size with
     # "Image.core.display_mode()[1]", but I think that's overkill...

Tests/test_file_pcx.py

@@ -2,29 +2,30 @@
 
 from PIL import Image
 
-def test_sanity():
-
-    file = tempfile("temp.pcx")
-
-    lena("1").save(file)
-
-    im = Image.open(file)
-    im.load()
-    assert_equal(im.mode, "1")
-    assert_equal(im.size, (128, 128))
-    assert_equal(im.format, "PCX")
-
-    lena("1").save(file)
-    im = Image.open(file)
-
-    lena("L").save(file)
-    im = Image.open(file)
 
-    lena("P").save(file)
-    im = Image.open(file)
+def _roundtrip(im):
+    f = tempfile("temp.pcx")
+    im.save(f)
+    im2 = Image.open(f)
 
-    lena("RGB").save(file)
-    im = Image.open(file)
+    assert_equal(im2.mode, im.mode)
+    assert_equal(im2.size, im.size)
+    assert_equal(im2.format, "PCX")
+    assert_image_equal(im2, im)
+
+def test_sanity():
+    for mode in ('1', 'L', 'P', 'RGB'):
+        _roundtrip(lena(mode))
+
+def test_odd():
+    # see issue #523, odd sized images should have a stride that's even.
+    # not that imagemagick or gimp write pcx that way. 
+    # we were not handling properly. 
+    for mode in ('1', 'L', 'P', 'RGB'):
+        # larger, odd sized images are better here to ensure that
+        # we handle interrupted scan lines properly.
+        _roundtrip(lena(mode).resize((511,511)))
+
 
 def test_pil184():
     # Check reading of files where xmin/xmax is not zero.