To use the Trace Bitmap function, simply select the object you’d like to trace, then go to Path > Trace Bitmap. The Trace Bitmap extension scans your image and uses it as a reference to automatically generate a vector rendering of it. The first way you can trace your PNG file is by using the Trace Bitmap function in Inkscape. The PNG format in and of itself is not capable of retaining such information.

The SVG is used as a reference to generate a series of static pixels that form the PNG file, and once that file is generated, the rest of the information from the SVG file (the mathematical formulas) is absent from it.

As I mentioned earlier, SVG files are what’s used to generate PNG files. I assume that the reason you’re trying to use Inkscape to convert PNG to SVG format is because you’d like to take advantage of these benefits. Since these formulas are far more dynamic than a series of static boxes, vector formats (like SVG) offer many more benefits, like being fully editable with vector graphics software, and having the ability to enlarge them infinitely without quality loss. Vector graphics (unlike raster graphics) are not made of pixels they’re made of mathematical formulas that dictate all of the properties of a graphic on an X and Y axis. The more you zoom in on them or try to enlarge them, the more visible the individual pixels become.

Graphics made of pixels are static and set at a specific size. png are raster graphics, meaning they’re made entirely of individual colored boxes known as pixels.

Inkscape png to svg command line