When we think about image viewers, we usually think about simple apps that allow you to, you know, view images, just like the ones most OSes pack by default.

Sensor data, advanced histograms, color maps, and a full set of useful statistics, are all features typically found in advanced image or video editors. However, there are a very small number of viewer apps that also include them, one of which is qv.

qv (short for quick view) is a free, open-source, Linux-only viewer for 2D data. It can be used to analyze images, sensor data, various types of renderings, simulations, and even videos.

The main reason you might want to use qv, as mentioned before, is that it provides a hefty set of tools for both image and video analysis. It's also as light and as almost as practical as a typical image viewer. This means that it works with most typical graphic formats, and it also allows you to load large numbers of pictures or videos.

Of course, for someone that's really trying to determine if a picture is or isn't what it should be, then the histogram, the pixel value inspector, the range selection, the dynamic range reduction, and value inspection tools are invaluable.

The short answer is, no, not at all. You could very well mistake it for a basic image viewer, up until the point where you actually load the provided tools.

Most of the app's tools can be easily accessed from the typical menubar, and all information is displayed at the bottom of the GUI. The Range and Colormap menus are by far the most important. The first allows you to toggle the histogram and visible range overlay, toggle the dynamic range reduction tool, as well as a lot of control over various values.  

The Colormap menu is the place from where you can toggle the colormap overlay as well as toggle between various colormaps (sequential, diverging, qualitative, and custom).

While it doesn't look the part, qv does bring to the table a set of very interesting features that are clearly not all that common for most viewer apps.