title: python PIL YCbCr support
body: <p>Trying to create an PIL image in YCbCr mode crashes even a fresh python/PIL installation from synaptic in my ubuntu 11.04 </p>
  
  <pre><code>wim@wim-ubuntu:~$ python
  Python 2.7.1+ (r271:86832, Apr 11 2011, 18:13:53) 
  [GCC 4.5.2] on linux2
  Type "help", "copyright", "credits" or "license" for more information.
  &gt;&gt;&gt; import Image
  &gt;&gt;&gt; Image.VERSION
  '1.1.7'
  &gt;&gt;&gt; Image.new('YCbCr', (640,480))
  *** buffer overflow detected ***: python terminated
  ======= Backtrace: =========
  /lib/x86_64-linux-gnu/libc.so.6(__fortify_fail+0x37)[0x7f4a35e4a1d7]
  /lib/x86_64-linux-gnu/libc.so.6(+0xfd0f0)[0x7f4a35e490f0]
  /usr/local/lib/python2.7/dist-packages/PIL/_imaging.so(ImagingNewPrologueSubtype+0x97)[0x7f4a34bfb257]
  /usr/local/lib/python2.7/dist-packages/PIL/_imaging.so(ImagingNewBlock+0xb)[0x7f4a34bfb78b]
  /usr/local/lib/python2.7/dist-packages/PIL/_imaging.so(ImagingNew+0x4c)[0x7f4a34bfb86c]
  /usr/local/lib/python2.7/dist-packages/PIL/_imaging.so(+0xfd22)[0x7f4a34bddd22]
  python(PyEval_EvalFrameEx+0x361)[0x4965f1]
  python(PyEval_EvalCodeEx+0x145)[0x49d325]
  python(PyEval_EvalFrameEx+0x802)[0x496a92]
  python(PyEval_EvalCodeEx+0x145)[0x49d325]
  python(PyEval_EvalCode+0x32)[0x4ecb02]
  python[0x4fdc74]
  python(PyRun_InteractiveOneFlags+0x1e2)[0x42cd9e]
  python(PyRun_InteractiveLoopFlags+0xc0)[0x42cebd]
  python(PyRun_AnyFileExFlags+0x39)[0x42d2e1]
  python(Py_Main+0xac9)[0x418c9e]
  /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xff)[0x7f4a35d6aeff]
  python[0x4c62b1]
  ======= Memory map: ========
  00400000-0062f000 r-xp 00000000 08:21 1049585                            /usr/bin/python2.7
  0082e000-0082f000 r--p 0022e000 08:21 1049585                            /usr/bin/python2.7
  0082f000-00897000 rw-p 0022f000 08:21 1049585                            /usr/bin/python2.7
  00897000-008a9000 rw-p 00000000 00:00 0 
  01f0a000-021a1000 rw-p 00000000 00:00 0                                  [heap]
  7f4a34794000-7f4a347a9000 r-xp 00000000 08:21 659235                     /lib/x86_64-linux-gnu/libgcc_s.so.1
  7f4a347a9000-7f4a349a8000 ---p 00015000 08:21 659235                     /lib/x86_64-linux-gnu/libgcc_s.so.1
  7f4a349a8000-7f4a349a9000 r--p 00014000 08:21 659235                     /lib/x86_64-linux-gnu/libgcc_s.so.1
  7f4a349a9000-7f4a349aa000 rw-p 00015000 08:21 659235                     /lib/x86_64-linux-gnu/libgcc_s.so.1
  7f4a349aa000-7f4a349cd000 r-xp 00000000 08:21 1057568                    /usr/lib/x86_64-linux-gnu/libjpeg.so.62.0.0
  7f4a349cd000-7f4a34bcc000 ---p 00023000 08:21 1057568                    /usr/lib/x86_64-linux-gnu/libjpeg.so.62.0.0
  7f4a34bcc000-7f4a34bcd000 r--p 00022000 08:21 1057568                    /usr/lib/x86_64-linux-gnu/libjpeg.so.62.0.0
  7f4a34bcd000-7f4a34bce000 rw-p 00023000 08:21 1057568                    /usr/lib/x86_64-linux-gnu/libjpeg.so.62.0.0
  7f4a34bce000-7f4a34c0b000 r-xp 00000000 08:21 1312337                    /usr/local/lib/python2.7/dist-packages/PIL/_imaging.so
  7f4a34c0b000-7f4a34e0b000 ---p 0003d000 08:21 1312337                    /usr/local/lib/python2.7/dist-packages/PIL/_imaging.so
  7f4a34e0b000-7f4a34e0e000 r--p 0003d000 08:21 1312337                    /usr/local/lib/python2.7/dist-packages/PIL/_imaging.so
  7f4a34e0e000-7f4a34e11000 rw-p 00040000 08:21 1312337                    /usr/local/lib/python2.7/dist-packages/PIL/_imaging.so
  7f4a34e11000-7f4a34e30000 r-xp 00000000 08:21 1316665                    /usr/lib/python2.7/lib-dynload/_ctypes.so
  7f4a34e30000-7f4a3502f000 ---p 0001f000 08:21 1316665                    /usr/lib/python2.7/lib-dynload/_ctypes.so
  7f4a3502f000-7f4a35030000 r--p 0001e000 08:21 1316665                    /usr/lib/python2.7/lib-dynload/_ctypes.so
  7f4a35030000-7f4a35034000 rw-p 0001f000 08:21 1316665                    /usr/lib/python2.7/lib-dynload/_ctypes.so
  7f4a35034000-7f4a35035000 rw-p 00000000 00:00 0 
  7f4a35035000-7f4a35075000 r-xp 00000000 08:21 655419                     /lib/libncurses.so.5.7
  7f4a35075000-7f4a35274000 ---p 00040000 08:21 655419                     /lib/libncurses.so.5.7
  7f4a35274000-7f4a35278000 r--p 0003f000 08:21 655419                     /lib/libncurses.so.5.7
  7f4a35278000-7f4a35279000 rw-p 00043000 08:21 655419                     /lib/libncurses.so.5.7
  7f4a35279000-7f4a352b2000 r-xp 00000000 08:21 655450                     /lib/libreadline.so.6.2
  7f4a352b2000-7f4a354b2000 ---p 00039000 08:21 655450                     /lib/libreadline.so.6.2
  7f4a354b2000-7f4a354b4000 r--p 00039000 08:21 655450                     /lib/libreadline.so.6.2
  7f4a354b4000-7f4a354ba000 rw-p 0003b000 08:21 655450                     /lib/libreadline.so.6.2
  7f4a354ba000-7f4a354bb000 rw-p 00000000 00:00 0 
  7f4a354bb000-7f4a354c0000 r-xp 00000000 08:21 1316693                    /usr/lib/python2.7/lib-dynload/readline.so
  7f4a354c0000-7f4a356bf000 ---p 00005000 08:21 1316693                    /usr/lib/python2.7/lib-dynload/readline.so
  7f4a356bf000-7f4a356c0000 r--p 00004000 08:21 1316693                    /usr/lib/python2.7/lib-dynload/readline.so
  7f4a356c0000-7f4a356c2000 rw-p 00005000 08:21 1316693                    /usr/lib/python2.7/lib-dynload/readline.so
  7f4a356c2000-7f4a35d4c000 r--p 00000000 08:21 1055991                    /usr/lib/locale/locale-archive
  7f4a35d4c000-7f4a35ed6000 r-xp 00000000 08:21 659207                     /lib/x86_64-linux-gnu/libc-2.13.so
  7f4a35ed6000-7f4a360d5000 ---p 0018a000 08:21 659207                     /lib/x86_64-linux-gnu/libc-2.13.so
  7f4a360d5000-7f4a360d9000 r--p 00189000 08:21 659207                     /lib/x86_64-linux-gnu/libc-2.13.so
  7f4a360d9000-7f4a360da000 rw-p 0018d000 08:21 659207                     /lib/x86_64-linux-gnu/libc-2.13.so
  7f4a360da000-7f4a360e0000 rw-p 00000000 00:00 0 
  7f4a360e0000-7f4a36164000 r-xp 00000000 08:21 659244                     /lib/x86_64-linux-gnu/libm-2.13.so
  7f4a36164000-7f4a36363000 ---p 00084000 08:21 659244                     /lib/x86_64-linux-gnu/libm-2.13.so
  7f4a36363000-7f4a36364000 r--p 00083000 08:21 659244                     /lib/x86_64-linux-gnu/libm-2.13.so
  7f4a36364000-7f4a36365000 rw-p 00084000 08:21 659244                     /lib/x86_64-linux-gnu/libm-2.13.so
  7f4a36365000-7f4a3637c000 r-xp 00000000 08:21 659290                     /lib/x86_64-linux-gnu/libz.so.1.2.3.4
  7f4a3637c000-7f4a3657b000 ---p 00017000 08:21 659290                     /lib/x86_64-linux-gnu/libz.so.1.2.3.4
  7f4a3657b000-7f4a3657c000 r--p 00016000 08:21 659290                     /lib/x86_64-linux-gnu/libz.so.1.2.3.4
  7f4a3657c000-7f4a3657d000 rw-p 00017000 08:21 659290                     /lib/x86_64-linux-gnu/libz.so.1.2.3.4
  7f4a3657d000-7f4a366e3000 r-xp 00000000 08:21 655398                     /lib/libcrypto.so.0.9.8
  7f4a366e3000-7f4a368e3000 ---p 00166000 08:21 655398                     /lib/libcrypto.so.0.9.8
  7f4a368e3000-7f4a368f0000 r--p 00166000 08:21 655398                     /lib/libcrypto.so.0.9.8
  7f4a368f0000-7f4a36909000 rw-p 00173000 08:21 655398                     /lib/libcrypto.so.0.9.8
  7f4a36909000-7f4a3690c000 rw-p 00000000 00:00 0 
  7f4a3690c000-7f4a36958000 r-xp 00000000 08:21 655454                     /lib/libssl.so.0.9.8Aborted
  wim@wim-ubuntu:~$ 
  </code></pre>
  
  <p>I've tried </p>
  
  <pre><code>find /usr -name Image.py | xargs grep -n YCbCr 
  </code></pre>
  
  <p>and found what I believe to be the offending line </p>
  
  <pre><code>216:    "YCbCr": ('|u1', 4),
  </code></pre>
  
  <p>YCbCr images should be 3 channel, not 4.  I changed this to 3 and deleted the .pyc, but the code still crashed in the same way when it goes into the c code (core.fill with mode='YCbCr').  OK so I thought maybe the error worked its way into the build somehow, marked PIL for complete removal in package manager, downloaded the sources, dependencies, and modified that number 4 to 3, and after a bit of mucking around with paths was able to build PIL again, with all the selftests passing, then installing.  Unfortunately, still the same crash.  Now I'm at a loss at to what to do - I need YCbCr colour space support in PIL but can't fix the bug. </p>
  
  <p>edit:  perhaps this can provide further insight, I've found that while <code>Image.new('YCbCr', (640,480))</code> did not crash in 10.10, it can be provoked to segfault by using <code>numpy.asarray(Image.new('YCbCr', (640,480)))</code>.  It all smells like a memory problem in some C-extension of numpy and/or PIL, or the way they are talking to each other.  </p>