3mfthumb

Extract thumbnail images from 3MF files and display them in file managers.

Preview images are great. As .3mf is supposed to be the universal 3D Printing standard, and adoption is expected to be rapid, we should be able to see embedded thumbnail image previews for them in file managers like pcmanfm, nautilus, or even Windows explorer.

Get it from GitHub

git clone https://github.com/themanyone/3mfthumb.git
cd 3mfthumb

Install dependencies

Fedora, Centos. dnf install libzip-devel lib3mf-devel zlib-devel

Ubuntu, Debian. dpkg -i libzip-dev lib3mf-dev zlib1g-dev

Arch pacman -S libzip lib3mf zlib1g

We will assume you have a build environment such as gcc-c++, pkg-config and make.

Build

make
make install

Now log out of the desktop session (or reboot).

Multi-user environments. Please do not use sudo make install unless the system has multiple graphical desktop users. In that case, you may edit Makefile to change DESTDIR to INSTALL_ROOT. And manually remove old thumbnails for each user: rm -rf $(HOME)/.cache/thumbnails/*.

Configure file manager preferences to show previews for files > 1MB.

make uninstall to remove these components if no longer needed.

Developer logic

The current version of the Lib3MF API uses the lib3mf_implicit.hpp header file instead of Lib3MF_Resources.hpp. This newer API provides a more simplified interface for working with the Lib3MF library.

This code uses the CWrapper::loadLibrary() method to load the Lib3MF library and create a new model. It then uses the QueryReader() method to create a new reader for the 3MF file format and read the model from a file using ReadFromFile(). Finally, we use the HasPackageThumbnailAttachment() and GetPackageThumbnailAttachment() methods to retrieve the thumbnail attachment and write it to a file using WriteToFile().

Build problems

The Makefile uses pkg-config --cflags --libs lib3mf to obtain the compiler flags to use. In particular, the location of lib3mf_implicit.hpp. If for some reason your system does not have pkg-config, you might be able to substitute these into the Makefile.

BUILD_CFLAGS=-I/usr/include/lib3mf LDFLAGS:=-l3mf -lzip -lz

On Arch, lib3mf-dev may not be properly installed. The build script forgot to create simlinks to the C bindings. It should be filed as a bug. A command such as th following might work around the issue.

ln -s /usr/include/lib3mf/Bindings/Cpp/* /usr/include/lib3mf/

Cross compiling to Windows

To build for Windows, first install dependencies. Use the package manager to install mingw64-gcc-g++, mingw64-zlib, and mingw64-libzip. Now we need the lib3mf.dll, available from https://github.com/3MFConsortium/lib3mf/releases like so.

wget https://github.com/3MFConsortium/lib3mf/releases/download/v2.2.0/lib3mf_sdk_v2.2.0.zip
unzip lib3mf_sdk_v2.2.0.zip

Now use mingw64-make to build the windows executable, emfthumb.exe. Set LIBS to the location of the extracted lib3mf/Lib dir, which should already contain a precompiled library lib3mf.dll.

LIBS=-L/home/k/Downloads/src/lib3mf/Lib mingw64-make

Windows install

Copy 3mfthumb.exe along with lib3mf.dll to somewhere on the Windows machine. Maybe in C:\Program Files

In theory, we can use regedit to designate 3mfthumb.exe as the preferred handler to generate image previews for .3mf files. ChatGPT suggested something similar to the following. If it doesn't work, you can ask ChatGPT or Bing to fix it up.

Open the Registry Editor by typing "regedit" in the Windows search bar and selecting "Registry Editor".
Navigate to HKEY_CLASSES_ROOT.3mf.
Right-click on something like "ThumbnailHandler" and select "Modify".
Set the value data to the full path of 3mfthumb.exe (e.g. "C:\Program Files\3mfthumb.exe") and click "OK".
Close the Registry Editor.

If it works, when you navigate to a folder containing a .3mf file, Windows should generate a thumbnail using 3mfthumb.exe.

Issues

We are new to C++ development, so there are bound to be some problems. Image previews have not been tested on Windows yet. But we're working on it. Discuss issues on the GitHub issue tracker.

Author's links

- GitHub https://github.com/themanyone
- YouTube https://www.youtube.com/themanyone
- Mastodon https://mastodon.social/@themanyone
- Linkedin https://www.linkedin.com/in/henry-kroll-iii-93860426/
- [TheNerdShow.com](http://thenerdshow.com/)