DIPlib Build on Windows/MSVC: PyDIP Issue

[AleksandraWill]

Component
PyDIP / CMake build scripts.
The DIPlib source code as of 19-07-2025.

Describe the bug
PyDIP check MSB8066

36>[doctest] test cases:  104 |  104 passed | 0 failed | 0 skipped
36>[doctest] assertions: 3684 | 3684 passed | 0 failed |
36>[doctest] Status: SUCCESS!
36>Building Custom Rule C:/Users/Aleksandra/Libraries/diplib/src/CMakeLists.txt
41>PyDIPjavaio.vcxproj -> C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\PyDIPjavaio.cp312-win_amd64.pyd
14>PyDIP_bin.vcxproj -> C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\PyDIP_bin.cp312-win_amd64.pyd
38>Finished generating code
38>PyDIPviewer.vcxproj -> C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\PyDIPviewer.cp312-win_amd64.pyd
42>------ Build started: Project: PyDIP, Configuration: Release x64 ------
43>------ Build started: Project: ALL_BUILD, Configuration: Release x64 ------
42>1>
42>Building Custom Rule C:/Users/Aleksandra/Libraries/diplib/pydip/CMakeLists.txt
43>Building Custom Rule C:/Users/Aleksandra/Libraries/diplib/CMakeLists.txt
44>------ Build started: Project: staging, Configuration: Release x64 ------
45>------ Skipped Build: Project: INSTALL, Configuration: Release x64 ------
45>Project not selected to build for this solution configuration 
44>1>
44>Building Custom Rule C:/Users/Aleksandra/Libraries/diplib/pydip/CMakeLists.txt
46>------ Build started: Project: bdist_wheel, Configuration: Release x64 ------
47>------ Build started: Project: PyDIP_check, Configuration: Release x64 ------
47>1>
47>Could not load PyDIP binary extension. Did you install the Microsoft Visual C++ Redistributable?
47>Traceback (most recent call last):
47>  File "C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\unit_tests.py", line 20, in <module>
47>    import staging.diplib
47>  File "C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\staging\diplib\__init__.py", line 39, in <module>
47>    from .PyDIP_bin import *
47>ImportError: DLL load failed while importing PyDIP_bin: Nie mo┐na odnalečŠ okreťlonego modu│u.
47>The system cannot find the batch label specified - VCEnd
47>C:\Program Files\Microsoft Visual Studio\2022\Community\MSBuild\Microsoft\VC\v170\Microsoft.CppCommon.targets(237,5): error MSB8066: Custom build for 'C:\Users\Aleksandra\Libraries\diplib\build\CMakeFiles\7230119ff65d6f90253a09b4db4b6fb9\PyDIP_check.rule' exited with code 1.
47>Done building project "PyDIP_check.vcxproj" -- FAILED.
48>------ Skipped Build: Project: check, Configuration: Release x64 ------
48>Project not selected to build for this solution configuration 
46>1>
46>* Getting build dependencies for wheel...
46>C:\Users\Aleksandra\Libraries\python_libs\env_312\Lib\site-packages\setuptools\command\bdist_wheel.py:103: RuntimeWarning: Config variable 'Py_DEBUG' is unset, Python ABI tag may be incorrect
46>  if get_flag("Py_DEBUG", hasattr(sys, "gettotalrefcount"), warn=(impl == "cp")):

To Reproduce
configuration in CMake GUI:

DIPlib-CMake-configuration-report.txt

I modified CMakeLists.txt files during the DipLib build, in part because Vigra was previously built with OpenEXR.
A linking error with the source-built FreeType was resolved by linking the Vcpkg-installed FreeType library.

• root/CMakeLists.txt:

# OpenMP
find_package(OpenMP)
if(OpenMP_CXX_FOUND OR OPENMP_FOUND) # OPENMP_FOUND for CMake <= 3.8
   set(DIP_ENABLE_MULTITHREADING ON CACHE BOOL "Enable multithreading support")
endif()

# Add this here:
find_package(OpenEXR REQUIRED)
find_package(Freetype REQUIRED)

include(${CMAKE_CURRENT_LIST_DIR}/tools/compiler_flags.cmake)
include(${CMAKE_CURRENT_LIST_DIR}/tools/update_deps_file.cmake)

• src/CMakeLists.xt

# Use FreeType
find_package(Freetype)
if(FREETYPE_FOUND)
   set(DIP_ENABLE_FREETYPE ON CACHE BOOL "Enable linking against FreeType, for better text rendering in images")
else()
   set(DIP_ENABLE_FREETYPE OFF CACHE BOOL "Enable linking against FreeType, for better text rendering in images")
endif()
if(DIP_ENABLE_FREETYPE)
   target_include_directories(DIP PRIVATE ${FREETYPE_INCLUDE_DIRS})
   target_link_libraries(DIP PRIVATE Freetype::Freetype)
   target_compile_definitions(DIP PRIVATE DIP_CONFIG_HAS_FREETYPE)
endif()

I have modified file:

• src\library\physical_dimensions.cpp (lines 518-623):

#ifdef DIP_CONFIG_ENABLE_UNICODE

      dip::Units f = dip::Units::Meter();
      DOCTEST_CHECK(( f ).String() == "m" );
      DOCTEST_CHECK(( f ).StringUnicode() == "m" );
      DOCTEST_CHECK(( f * f ).String() == "m^2" );
      DOCTEST_CHECK(( f * f ).StringUnicode() == u8"m\u00B2" );
      DOCTEST_CHECK(( f * f * f ).String() == "m^3" );
      DOCTEST_CHECK(( f * f * f ).StringUnicode() == u8"m\u00B3" );
      DOCTEST_CHECK(( f * f * f * f ).String() == "m^4" );
      DOCTEST_CHECK(( f * f * f * f ).StringUnicode() == u8"m\u2074" );
      DOCTEST_CHECK(( dip::Units() / f ).String() == "m^-1" );
      DOCTEST_CHECK(( dip::Units() / f ).StringUnicode() == u8"m\u207B\u00B9" );
      DOCTEST_CHECK(( dip::Units() / f / f ).String() == "m^-2" );
      DOCTEST_CHECK(( dip::Units() / f / f ).StringUnicode() == u8"m\u207B\u00B2" );
      DOCTEST_CHECK(( dip::Units() / f / f / f ).String() == "m^-3" );
      DOCTEST_CHECK(( dip::Units() / f / f / f ).StringUnicode() == u8"m\u207B\u00B3" );
      DOCTEST_CHECK(( dip::Units() / f / f / f / f ).String() == "m^-4" );
      DOCTEST_CHECK(( dip::Units() / f / f / f / f ).StringUnicode() == u8"m\u207B\u2074" );
      DOCTEST_CHECK( f == dip::Units( "m" ));
      DOCTEST_CHECK( f * f == dip::Units( "m^2" ));
      DOCTEST_CHECK( f * f == dip::Units( "m^2" ));
      DOCTEST_CHECK( f * f * f == dip::Units( "m^3" ));
      DOCTEST_CHECK( f * f * f == dip::Units( "m^3" ));
      DOCTEST_CHECK( f * f * f * f == dip::Units( "m^4" ));
      DOCTEST_CHECK( f * f * f * f == dip::Units( "m^4" ));
      DOCTEST_CHECK( dip::Units() / f == dip::Units( "m^-1" ));
      DOCTEST_CHECK( dip::Units() / f == dip::Units( "m^-1" ));
      DOCTEST_CHECK( dip::Units() / f / f == dip::Units( "m^-2" ));
      DOCTEST_CHECK( dip::Units() / f / f == dip::Units( "m^-2" ));
      DOCTEST_CHECK( dip::Units() / f / f / f == dip::Units( "m^-3" ));
      DOCTEST_CHECK( dip::Units() / f / f / f == dip::Units( "m^-3" ));
      DOCTEST_CHECK( dip::Units() / f / f / f / f == dip::Units( "m^-4" ));
      DOCTEST_CHECK( dip::Units() / f / f / f / f == dip::Units( "m^-4" ));

      dip::Units g = dip::Units::Second();
      DOCTEST_CHECK(( f / g ).String() == "m/s" );
      DOCTEST_CHECK(( f / g ).StringUnicode() == "m/s" );
      DOCTEST_CHECK(( f / g / g ).String() == "m/s^2" );
      DOCTEST_CHECK(( f / g / g ).StringUnicode() == u8"m/s\u00B2" );
      DOCTEST_CHECK(( f / g / g / g ).String() == "m/s^3" );
      DOCTEST_CHECK(( f / g / g / g ).StringUnicode() == u8"m/s\u00B3" );
      DOCTEST_CHECK(( f / g / g / g / g ).String() == "m/s^4" );
      DOCTEST_CHECK(( f / g / g / g / g ).StringUnicode() == u8"m/s\u2074" );
      DOCTEST_CHECK(( g / f ).String() == "s/m" );
      DOCTEST_CHECK(( g / f ).StringUnicode() == "s/m" );
      DOCTEST_CHECK(( g / f / f ).String() == "s/m^2" );
      DOCTEST_CHECK(( g / f / f ).StringUnicode() == u8"s/m\u00B2" );
      DOCTEST_CHECK(( g * g / f ).String() == "s^2/m" );
      DOCTEST_CHECK(( g * g / f ).StringUnicode() == u8"s\u00B2/m" );
      DOCTEST_CHECK(( g * f ).String() == "m.s" );
      DOCTEST_CHECK(( g * f ).StringUnicode() == u8"m\u00B7s" );
      DOCTEST_CHECK( f / g == dip::Units( "m/s" ));
      DOCTEST_CHECK( f / g / g == dip::Units( "m/s^2" ));
      DOCTEST_CHECK( f / g / g == dip::Units( "m/s^2" ));
      DOCTEST_CHECK( f / g / g / g == dip::Units( "m/s^3" ));
      DOCTEST_CHECK( f / g / g / g == dip::Units( "m/s^3" ));
      DOCTEST_CHECK( f / g / g / g / g == dip::Units( "m/s^4" ));
      DOCTEST_CHECK( f / g / g / g / g == dip::Units( "m/s^4" ));
      DOCTEST_CHECK( g / f == dip::Units( "s/m" ));
      DOCTEST_CHECK( g / f / f == dip::Units( "s/m^2" ));
      DOCTEST_CHECK( g / f / f == dip::Units( "s/m^2" ));
      DOCTEST_CHECK( g * g / f == dip::Units( "s^2/m" ));
      DOCTEST_CHECK( g * g / f == dip::Units( "s^2/m" ));
      DOCTEST_CHECK( g * f == dip::Units( "m.s" ));
      DOCTEST_CHECK( g * f == dip::Units( "m.s" ));

      DOCTEST_CHECK(( dip::Units::Millimeter() ).String() == "mm" );
      DOCTEST_CHECK(( dip::Units::Millimeter() ).StringUnicode() == "mm" );
      DOCTEST_CHECK(( dip::Units::Millimeter() * dip::Units::Millimeter() ).String() == "mm^2" );
      DOCTEST_CHECK(( dip::Units::Millimeter() * dip::Units::Millimeter() ).StringUnicode() == u8"mm\u00B2" );
      DOCTEST_CHECK(( dip::Units::Millimeter() * dip::Units::Meter() ).String() == "10^3.mm^2" );
      DOCTEST_CHECK(( dip::Units::Millimeter() * dip::Units::Meter() ).StringUnicode() == u8"10\u00B3\u00B7mm\u00B2" );
      DOCTEST_CHECK(( dip::Units::Kilometer() * dip::Units::Meter() ).String() == "10^3.m^2" );
      DOCTEST_CHECK(( dip::Units::Kilometer() * dip::Units::Meter() ).StringUnicode() == u8"10\u00B3\u00B7m\u00B2" );
      DOCTEST_CHECK( dip::Units::Millimeter() == dip::Units( "mm" ));
      DOCTEST_CHECK( dip::Units::Millimeter() * dip::Units::Millimeter() == dip::Units( "mm^2" ));
      DOCTEST_CHECK( dip::Units::Millimeter() * dip::Units::Millimeter() == dip::Units( "mm^2" ));
      DOCTEST_CHECK( dip::Units::Millimeter() * dip::Units::Meter() == dip::Units( "10^3.mm^2" ));
      DOCTEST_CHECK( dip::Units::Millimeter() * dip::Units::Meter() == dip::Units( "10^3.mm^2" ));
      DOCTEST_CHECK( dip::Units::Kilometer() * dip::Units::Meter() == dip::Units( "10^3.m^2" ));
      DOCTEST_CHECK( dip::Units::Kilometer() * dip::Units::Meter() == dip::Units( "10^3.m^2" ));

      DOCTEST_CHECK(( dip::Units( "10^6.mm^2" )).String() == "m^2" );
      DOCTEST_CHECK(( dip::Units( "10^6.mm^2" )).StringUnicode() == u8"m\u00B2" );

      DOCTEST_CHECK(( dip::Units( "km/s" )).String() == "km/s" );
      DOCTEST_CHECK(( dip::Units( "km/s" )).StringUnicode() == "km/s" );
      DOCTEST_CHECK(( dip::Units( "km.cd.rad.px" )).String() == "km.cd.rad.px" );
      DOCTEST_CHECK(( dip::Units( "km.cd.rad.px" )).StringUnicode() == u8"km\u00B7cd\u00B7rad\u00B7px" );
      DOCTEST_CHECK(( dip::Units( u8"km\u00B7cd\u00B7rad\u00B7px" )).StringUnicode() == u8"km\u00B7cd\u00B7rad\u00B7px" );
      DOCTEST_CHECK(( dip::Units( "km.cd/rad.px" )).String() == "km.cd.px/rad" );
      DOCTEST_CHECK(( dip::Units( "km.cd/rad.px" )).StringUnicode() == u8"km\u00B7cd\u00B7px/rad" );
      DOCTEST_CHECK(( dip::Units( u8"km\u00B7cd/rad\u00B7px" )).StringUnicode() == u8"km\u00B7cd\u00B7px/rad" );
      DOCTEST_CHECK(( dip::Units( "10^3.km^-1.cd^-2/K" )).String() == "m^-1/K/cd^2" );
      DOCTEST_CHECK(( dip::Units( "10^3.km^-1.cd^-2/K" )).StringUnicode() == u8"m\u207B\u00B9/K/cd\u00B2" );

      DOCTEST_CHECK_THROWS( dip::Units( "q" ));                // non-existing units
      DOCTEST_CHECK_THROWS( dip::Units( "m^2-" ));
      DOCTEST_CHECK_THROWS( dip::Units( "m^2-" ));  // m^2-
      DOCTEST_CHECK_THROWS( dip::Units( "m^-" ));
      DOCTEST_CHECK_THROWS( dip::Units( "m^-" ));        // m^-
      DOCTEST_CHECK_THROWS( dip::Units( "uum" ));
      DOCTEST_CHECK_THROWS( dip::Units( "uum" ));  // uum

#else

Python libraries:
requirements.txt

Libraries installed via .\vcpkg install in manifest mode:
vcpkg.json

System information:

• Windows 11 Home, 24H2
• Python 3.12.10
• MATLAB Version: 24.2.0.2806996 (R2024b) Update 3
• Microsoft Visual Studio Community 2022 (64-bit) - Current Version 17.14.12

VisualStudio.17.Release/17.14.12+36408.4
Microsoft .NET Framework
Version 4.8.09032
Installed Version: Community
Visual C++ 2022   00482-90000-00000-AA424
ASP.NET and Web Tools   17.14.122.59099
Azure App Service Tools v3.0.0   17.14.122.59099
C# Tools   4.14.0-3.25359.3+6dbcfd2f553ef1ef0ac48878ab17d18c1360735d
Common Azure Tools   1.10
Cookiecutter   17.0.25079.8
GitHub Copilot   17.14.995.13737
IncrediBuild Build Acceleration   1.6.0.7
Intel® C++ Compiler   2025.2
Intel® DPC++ Compatibility Tool   2025.2
Intel® oneAPI DPC++ Compiler   2025.2
Intel® oneAPI Menu & Samples   10.10.392.9731
Intel® Performance Libraries   2025.2
Intel® VTune™ Profiler 2025   1.3.39
Linux Core Dump Debugging   1.0.9.36401
Microsoft Azure Tools for Visual Studio   2.9
Microsoft JVM Debugger   1.0
NuGet Package Manager   6.14.1
Python - Profiling support   17.0.25079.8
Python - VC Project Support   17.0.23055.1
Python with Pylance   17.0.25079.8
Razor (ASP.NET Core)   17.14.3.2530601+3372435431977e91904a23ceb1eab689badc1bd9
SQL Server Data Tools   17.14.26.0
Test Adapter for Boost.Test   1.0
Test Adapter for Google Test   1.0
TypeScript Tools   17.0.40502.2001
Visual Basic Tools   4.14.0-3.25359.3+6dbcfd2f553ef1ef0ac48878ab17d18c1360735d
Visual C++ for Linux and Mac Development   1.0.9.36401
Visual F# Tools   17.14.0-beta.25230.7+c1a9d78ad4a474a716ccffb4367ed5151e3f7c9f
Visual Studio IntelliCode   2.2

[crisluengo]

It looks like the PyDIP DLL cannot find the DIPlib DLL. Not sure why this happened.

Try running the INSTALL target before running the CHECK target, see if that solves the issue.

[AleksandraWill]

I have reviewed your suggestion and executed the INSTALL target prior to running PyDIP_check. While this resolved the warning issues, the primary error persists.

Here is a screenshot showing the folder contents:

zlib1.dll is copied automatically by vcpkg's MSBuild/CMake "applocal" script...

Then, I manually copied the following files:

• DIP.DLL from diplib\build\pydip\Release\staging\diplib to diplib\build\pydip\Release folder and
• fftw3.dll and fftw3f.dll from C:\Users\Aleksandra\Libraries\vcpkg\vcpkg_installed\x64-windows\bin to diplib\build\pydip\Release

After re-running PyDIP_check, the original error remained. I then analyzed PyDIP_bin.cp312-win_amd64.pyd using Dependency Walker, and the output is shown below:

[crisluengo]

The original error was

47>------ Build started: Project: PyDIP_check, Configuration: Release x64 ------
47>1>
47>Could not load PyDIP binary extension. Did you install the Microsoft Visual C++ Redistributable?
47>Traceback (most recent call last):
47>  File "C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\unit_tests.py", line 20, in <module>
47>    import staging.diplib
47>  File "C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\staging\diplib\__init__.py", line 39, in <module>
47>    from .PyDIP_bin import *
47>ImportError: DLL load failed while importing PyDIP_bin: Nie mo┐na odnalečŠ okreťlonego modu│u.
47>The system cannot find the batch label specified - VCEnd
47>C:\Program Files\Microsoft Visual Studio\2022\Community\MSBuild\Microsoft\VC\v170\Microsoft.CppCommon.targets(237,5): error MSB8066: Custom build for 'C:\Users\Aleksandra\Libraries\diplib\build\CMakeFiles\7230119ff65d6f90253a09b4db4b6fb9\PyDIP_check.rule' exited with code 1.
47>Done building project "PyDIP_check.vcxproj" -- FAILED.

Here I see "DLL load failed while importing PyDIP_bin", though it doesn't give more details than that. Do you still see this same error message? Your Dependency Walker output looks fine ("API-MS-WIN..." files always show up as errors, not sure what that is about, but doesn't seem to be a problem).

[AleksandraWill]

I have the same error after moving the files...

I ran the command:

PS C:\Users\Aleksandra\Libraries\vcpkg> .\vcpkg integrate install
Applied user-wide integration for this vcpkg root.
CMake projects should use: "-DCMAKE_TOOLCHAIN_FILE=C:/Users/Aleksandra/Libraries/vcpkg/scripts/buildsystems/vcpkg.cmake"

All MSBuild C++ projects can now #include any installed libraries. Linking will be handled automatically. Installing new libraries will make them instantly available.

However, this did not resolve the issue.

I then modified the diplib\pydip\CMakeLists.txt file as follows:

# Build PyDIP_bin
pybind11_add_module(PyDIP_bin ${DIP_PYTHON_SRC})
target_link_libraries(PyDIP_bin PRIVATE DIP)
set_target_properties(PyDIP_bin PROPERTIES INSTALL_RPATH "${rpath}")

if(WIN32)
    add_custom_command(TARGET PyDIP_bin POST_BUILD
        COMMAND ${CMAKE_COMMAND} -E copy_if_different
            "$<TARGET_FILE:DIP>"
            "$<TARGET_FILE_DIR:PyDIP_bin>"
    )
endif()

This modification only allowed me to move the DIP.DLL file.

I am unsure how to solve the problem of the PyDIP_bin module failing to load because of a missing DLL dependency.

Here's what's in my folders:

[AleksandraWill]

Okay, I did something a bit careless... I unchecked PYBIND11_INSTALL. So, I did it again, this time making sure that PYBIND11_INSTALL is checked because it automatically includes USE_PYTHON_INCLUDE_DIRS (which is also checked).

I ranINSTALL-> Build, then I ran PyDIP_check ->Build, and finally I ran .\vcpkg integrate install
This allows me to have all the required .dll files in the release folder (with the additional DIP.DLL copy modification in CMakeLists.txt as described before).

the staging folder:

then I ran PyDIP_check ->Rebuild, and the error stays the same:

16>Could not load PyDIP binary extension. Did you install the Microsoft Visual C++ Redistributable?
16>Traceback (most recent call last):
16>  File "C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\unit_tests.py", line 20, in <module>
16>    import staging.diplib
16>  File "C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\staging\diplib\__init__.py", line 39, in <module>
16>    from .PyDIP_bin import *
16>ImportError: DLL load failed while importing PyDIP_bin: Nie mo┐na odnalečŠ okreťlonego modu│u.
16>The system cannot find the batch label specified - VCEnd

[AleksandraWill]

I enabled one more option in the CMake GUI: X_VCPKG_APPLOCAL_DEPS_INSTALL
I add this directory to Windows PATH environment variable: C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.44.35207\bin\Hostx64\x64\dumpbin.exe
I was testing the following:

• First, I ran these commands (I am not sure which one worked):

PS C:\Users\Aleksandra\Libraries\vcpkg> $targetPath = "C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\PyDIP_bin.cp312-win_amd64.pyd"
PS C:\Users\Aleksandra\Libraries\vcpkg> $applocal = "C:\Users\Aleksandra\Libraries\vcpkg\scripts\buildsystems\msbuild\applocal.ps1"
PS C:\Users\Aleksandra\Libraries\vcpkg> powershell -ExecutionPolicy Bypass -File $applocal -targetBinary $targetPath -installedDir "C:\Users\Aleksandra\Libraries\vcpkg\vcpkg_installed\x64-windows"
PS C:\Users\Aleksandra\Libraries\vcpkg> $targetPath = "C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release\PyDIP_check.exe"
PS C:\Users\Aleksandra\Libraries\vcpkg> $applocal = "C:\Users\Aleksandra\Libraries\vcpkg\scripts\buildsystems\msbuild\applocal.ps1"
PS C:\Users\Aleksandra\Libraries\vcpkg> powershell -ExecutionPolicy Bypass -File $applocal -targetBinary $targetPath -installedDir "C:\Users\Aleksandra\Libraries\vcpkg\vcpkg_installed\x64-windows"
PS C:\Users\Aleksandra> $env:PATH="C:\Users\Aleksandra\Libraries\diplib\build\pydip\Release;C:\Users\Aleksandra\Libraries\vcpkg\vcpkg_installed\x64-windows\bin;$env:PATH"

and then, I rebuild PyDIP_check (so that I have all required DLLs in the Release folder).

I am not sure what made the change, but before, DIPlib was not working from MATLAB. Now it looks like it works:

>> addpath('C:\Users\Aleksandra\Prefixes\DIPlib\share\DIPimage');
>> setenv('PATH',['C:\Users\Aleksandra\Prefixes\DIPlib\bin',';',getenv('PATH')]);
>> dipimage
 
   The image display windows you see now are created by dipinit.m.
   Type HELP DIPINIT to learn how to modify these default windows.

The issue remains; the only difference is that I can now use DIPlib from MATLAB

[crisluengo]

I honestly do not understand what is going on there. I don't use windows much at all, sorry for not being more useful in debugging this issue.

The checks pass on Windows in the CI, but there we build with minimal external dependencies (no FFTW, no FreeType, etc). And I would guess that one of those is the problem when failing to load the PyDIP binary, but the tests for DIPlib itself pass (that's the "36>[doctest] Status: SUCCESS!" line in your output). Somehow, within the Python environment, the system is not able to find the same libraries that it is able to find otherwise.

I would suggest running the INSTALL and the pip_install targets, then starting up Python normally and import diplib as dip. If that fails like it does during the check, use Dependency Walker on the PyDIP_bin binary that was installed (not the one in your build directory, the one under the Python packages). Hopefully that will give some more information about what is going wrong.

[crisluengo]

When running the automated tests, the package is created in the directory pydip/staging/diplib under your build directory. That is where you will find the PyDIP_bin binary that is being loaded by Python when you run the tests.

It is first built under <build>/pydip/, and it is copied into <build>/pydip/staging/diplib to run the test. Loading a binary like this can have different results depending on where it sits, as that affects the search path.

[AleksandraWill]

Okay, I did what you suggested and I think I've found the solution...

I have verified that VC++ is not a problem:

import ctypes
ctypes.CDLL("vcruntime140.dll")
<CDLL 'vcruntime140.dll', handle 7fff3ee80000 at 0x18ea36212b0>
ctypes.CDLL("msvcp140.dll")
<CDLL 'msvcp140.dll', handle 7fff463d0000 at 0x18ea35d43e0>

The only change I made was to line 28 in the diplib\pydip\src\ __init__.py.in file:
if os.name == "nt" and @pydip_wheel_include_libs@ == True:

I added C:\Users\Aleksandra\Prefixes\DIPlib\bin to the environment variables

The sequence of building the targets is INSTALL-> Build, then pip_install -> Build, then ALL_BUILD -> Build, PyDIPcheck -> Build
Or this sequence: INSTALL-> Build, then pip_install -> Build, then Solution 'DIPlib' -> Build, PyDIPcheck -> Build, INSTALL -> Rebuild

Normally, I would build a library by following these steps: Solution 'DIPlib' -> Build, INSTALL -> Build (as I did with Vigra or GLFW), but it does not work here

(env_312) PS C:\Users\Aleksandra\Libraries\python_libs\env_312> python
Python 3.12.10 (tags/v3.12.10:0cc8128, Apr  8 2025, 12:21:36) [MSC v.1943 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import diplib as dip
DIPlib -- a quantitative image analysis library
Version 3.5.2 (Aug 24 2025)
For more information see https://diplib.org
>>>