[pypy-dev] Issue #1779: im.point() 4000x slower than CPython (pypy/pypy)

[hugovk]

New issue 1779: im.point() 4000x slower than CPython
https://bitbucket.org/pypy/pypy/issue/1779/impoint-4000x-slower-than-cpython

hugovk:

The following code takes nearly 4000 times longer on PyPy 2.2.1 compared with CPython. It takes less than a second with CPython compared with over 5 minutes on PyPy:

```
#!/usr/bin/env python

from PIL import Image

im = Image.open("lena.ppm")

im.point(list(range(256))*3)
im.point(lambda x: x)

im = im.convert("I")
im.point(lambda x: x*1)
im.point(lambda x: x+1)
im.point(lambda x: x*1+1)

im.point(list(range(256))*256, 'L')
```
Test code:
https://github.com/hugovk/test/tree/484

```
2.6     0m0.098s
2.7     0m0.042s
3.2     0m0.106s
3.3     0m0.094s
3.4     0m0.069s
PyPy    5m16.867s
```
PyPy time / average CPython time = 3873.6797066

Timings from:
https://travis-ci.org/hugovk/test/builds/26190010

The code is a simplified form of a Pillow test. At the moment it is skipped for PyPy as it takes too long. No coverage is involved.

I've not tested on PyPy 2.3.