For those interested, Tonne Software (http://www.tonnesoftware.com/) among some other programs made a software to draw personalized meter scales. Unfortunately not open source but worth a look nonetheless.
I would love a library to implement virtual instruments (VU meters, ammeters, voltmeters, scales etc.) using most common graphic libraries, that is, an instrument "component" with a set of rules for its needle min-max values, speed, ratio, inertia etc, and some nicely drawn needles and background usages/styles to replicate vintage or modern instruments.
I admit having tried ages ago to do something similar in Delphi, a radio virtual scale, but failed badly: In my approach I tried to move the background (a scanned replica of a real radio scale) under a smaller window with fixed needle, but smoothness was terrible. Animating the needle would probably have been easier.
I built just that but for a platform that is no longer usable (Borland C++ builder). The whole idea of re-usable components like that which you include in your product linked along with the rest of the code was very appealing, much more so than today's 'include this javascript from some server somewhere'. At least we now have subsource integrity.
Note that there have been some recent changes—we now have LKFS, or LUFS, whatever you want to call it. There are now a set of standards for how to compare the loudness of different programs.
Nowadays there are enough systems out there that will clamp down on LUFS to some value like -14 that it’s taking away incentives for people to slam their mixes into the wall. Spotify does this. If your music is -8 LUFS the Spotify attenuates it by -6.
Unfortunately, the majority of technical details on the web on implementing VU meters in the digital domain is misleading, of not outright wrong.
A while back, I implemented VU meters for some professional AV software. I started with the available references, but quickly discovered that it was well-intentioned but incorrect/inaccurate. I ended up sourcing the original specification for the analog meters, and then devising digital filters to replicate the same ballistics. This matched perfectly with the reference, (pro hardware).
TL;DR don't believe what you read on the web. Go to primary sources!
I would love a library to implement virtual instruments (VU meters, ammeters, voltmeters, scales etc.) using most common graphic libraries, that is, an instrument "component" with a set of rules for its needle min-max values, speed, ratio, inertia etc, and some nicely drawn needles and background usages/styles to replicate vintage or modern instruments. I admit having tried ages ago to do something similar in Delphi, a radio virtual scale, but failed badly: In my approach I tried to move the background (a scanned replica of a real radio scale) under a smaller window with fixed needle, but smoothness was terrible. Animating the needle would probably have been easier.