Test Card can generate a test pattern image at any resolution and display it either fullscreen or in a window. It is also possible to save the currently displayed image to a file.
The image can be used to determine if your monitor (or e.g. a TV your computer is connected to) is displaying pixel perfect image or if it does something funky to it.
In 2016 I came across a 3840x2160 display and used it to extend the desktop on my laptop computer.
I noticed some colour artifacts in some places. These later proved to be chroma subsampling (as allowed by HDMI specs).
Looking for a test pattern I came across Väinö Helminen's http://vah.dy.fi/testcard/ .
It was nice but I noticed an issue: color lines that are so useful to exhibit the effect of chroma subsampling had a spatial period of 3 pixels, while IMHO only a period of 2 would very clearly show subsampling.
So I contacted the author, changed code and forked the original git repository on https://git.gizmo.dy.fi/testcard.git (no web view, just git clone to access it) to share modifications.
Visit http://vah.dy.fi/testcard/ for details, including keys (hint: F1-F4, s, q).
Test patterns clearly smudged when subsampling is enabled.now merged from original which has an interactive test- Option to use custom font (requested in issues). Use it like this:
./testcard -f /usr/share/fonts/truetype/msttcorefonts/impact.ttf
Test Card is released under the GNU General Public License, version 2.
- Original software by Väinö Helminen published on http://vah.dy.fi/testcard/ .
- Original git repository on https://git.gizmo.dy.fi/testcard.git (no web view, just
git cloneto access it).