ImportError: DLL load failed: The specified module could not be found (related to png16.dll)

I am still trying to build matplotlib on windows. The instructions on 1717 were very helpful, I managed to build the
prerequisites manually based on the instructions in the dep_build.cmd that came from matplotlib-winbuild project.

But when I try to run it I get this error message:

import matplotlib.pyplot as plt
Traceback (most recent call last):
File “”, line 1, in
File “C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\pyplot.py”, line 27, in

import matplotlib.colorbar

File “C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\colorbar.py”, line 34, in
import matplotlib.collections as collections

File “C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\collections.py”, line 27, in
import matplotlib.backend_bases as backend_bases
File “C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\backend_bases.py”, line 56, in

import matplotlib.textpath as textpath

File “C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\textpath.py”, line 22, in
from matplotlib.mathtext import MathTextParser

File “C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\mathtext.py”, line 63, in
import matplotlib._png as _png
ImportError: DLL load failed: The specified module could not be found.

I am guessing it doesn’t like the filename of the png16.dll file, but how do I know what filename it is looking for?
I noticed I had to rename a bunch of .lib files in order to build matplotlib from source, but that was OK since the error message

said what file it was looking for. How do I determine the correct filename to use from here?

It's better to use the static libraries for libpng, zlib, and freetype (unless you have reasons not to). Rename the .lib files as in the build script:

<https://github.com/jbmohler/matplotlib-winbuild/blob/master/build_dep.cmd#L236>
<https://github.com/jbmohler/matplotlib-winbuild/blob/master/build_dep.cmd#L214>
<https://github.com/jbmohler/matplotlib-winbuild/blob/master/build_dep.cmd#L247>

Christoph

···

On 7/2/2014 11:46 AM, Alan Ezust wrote:

I am still trying to build matplotlib on windows. The instructions on
1717 were very helpful, I managed to build the
prerequisites manually based on the instructions in the dep_build.cmd
that came from matplotlib-winbuild project.

But when I try to run it I get this error message:

import matplotlib.pyplot as plt

Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
   File
"C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\pyplot.py",
line 27, in <module>
     import matplotlib.colorbar
   File
"C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\colorbar.py",
line 34, in <module>
     import matplotlib.collections as collections
   File
"C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\collections.py",
line 27, in <module>
     import matplotlib.backend_bases as backend_bases
   File
"C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\backend_bases.py",
line 56, in <module>
     import matplotlib.textpath as textpath
   File
"C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\textpath.py",
line 22, in <module>
     from matplotlib.mathtext import MathTextParser
   File
"C:\Python33\lib\site-packages\matplotlib-1.4.x-py3.3-win32.egg\matplotlib\mathtext.py",
line 63, in <module>
     import matplotlib._png as _png
ImportError: DLL load failed: The specified module could not be found.

I am guessing it doesn't like the filename of the png16.dll file, but
how do I know what filename it is looking for?
I noticed I had to rename a bunch of .lib files in order to build
matplotlib from source, but that was OK since the error message
said what file it was looking for. How do I determine the correct
filename to use from here?