EliahKagan / ImageViewer

an, um, image viewer

Image Viewer - an, um, image viewer

Image Viewer is a picture viewing program that I wrote to learn PySide. If you’re learning it too, then you might… not really benefit much from this, since there are many image viewing sample programs written by people who already know what they’re doing.

Actually, my initial motivation was to have a simple cross-platform image viewer—other than my web browser—that could open .webp files, in addition to all the more long-standing image types. Qt’s QPixmap class automatically supports this, so one gets WebP support with no special effort, when writing an image viewer targeting Qt.

License

Image Viewer is licensed under 0BSD.

How to run it

Image Viewer should run on GNU/Linux systems (such as Ubuntu), Windows, and macOS. It depends on some other software, mainly PySide6. I suggest using a virtual environment with pipenv. To do that, install pipenv if you don’t have it, then from the top-level directory of this repository, run:

pipenv update

Then, to run Image Viewer:

pipenv run python viewer

(You can alternatively use pipenv run ./viewer, except on Windows.)

That opens a file picker dialog, in which you select a picture to open.

If you like, you can instead pass the path as a command-line argument, such as:

pipenv run python viewer unexpected-bobcat.webp

(Likewise, pipenv run ./viewer unexpected-bobcat.webp works except on Windows.)

If you're going to run Image Viewer multiple times in succession, you can have pipenv start you a shell:

pipenv shell

Then you can run it in the shell like this:

python viewer

(Though you’ll likely prefer simply ./viewer—except on Windows.)

To be reminded of how to run it:

python viewer --help

The libOpenGL.so.0 bug

Unfortunately, a bug in Qt gives an error on some systems:

ImportError: libOpenGL.so.0: cannot open shared object file: No such file or directory

If you see an error message that ends with that line, you'll have to install libOpenGL. How to do that varies across systems, but on Debian and Ubuntu, run:

sudo apt update
sudo apt install libopengl0

Then you should be able to run Image Viewer (and other PySide6 programs) without a crash.

Other dependency satisfaction bugs

Sometimes other libraries are needed. In particular, you may get:

t.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.

I don’t think this happens on Windows; if it does, I don’t know how to solve it there.

Otherwise, to find out how to fix it, re-run the command that produced that error with the QT_DEBUG_PLUGINS environment variable set to 1. For example, in a Bourne-style shell like bash or zsh, if you ran ./viewer, run:

QT_DEBUG_PLUGINS=1 ./viewer

Likewise, if you ran pipenv run ./viewer, run:

QT_DEBUG_PLUGINS=1 pipenv run ./viewer

This produces lots of output. Look near the end, just above the text that appeared before when you ran it without QT_DEBUG_PLUGINS=1, and look for an error message that ends like

(FILENAME: cannot open shared object file: No such file or directory)

but with some filename in place of FILENAME. For example:

Cannot load library /home/ek/.local/share/virtualenvs/ImageViewer-hsDVqvxw/lib/python3.9/site-packages/PySide6/Qt/plugins/platforms/libqxcb.so: (libxcb-icccm.so.4: cannot open shared object file: No such file or directory)

In that example, the file I needed was libxcb-icccm.so.4.

Then search for how to install the package that provides that file on your system. Depending on what system or (especially in the case of macOS) what third-party package manager you’re using, you may be able to do this directly from the package manager. Or you may be able to check online: for example, you can search the contents of packages for Debian or search the contents of packages for Ubuntu.

Then install that package and try again. You may be missing multiple libraries, but the error output will only tell you about one each time, so you may need to do it a few times.