The major problem with SVG is text computer fonts. If you make an image with text that depends on one computer font and it is not present in the viewer's machine, it will use some other font, which may overlap with other elements of the image. Some libraries Matplotlib solve this by writing characters as curves, but this produces large files and unsearchable text. The inability of different computer platforms to standardize fonts that must always be present is a major issue.

TODO:

Dropped in favor of SVG 2.

PNG reference implementation. Ahh, if feels good to have a dominating open source reference implementation.

Demo of using it by Ciro Santilli: stackoverflow.com/questions/1362945/how-to-decode-a-png-image-to-raw-bytes-from-c-code-with-libpng/36399711#36399711

It's not super easy to use at first.

And it sometimes says that the basic drawing thing you want to do is off the project's scope.

But as you learn more about it and further generalize the concepts, there are often reasonable reasons for those design choices.

And the UI looks good :-)

Examples:

Some answers by Ciro Santilli:

Generally means that he form of the equation $f(x)$ does not change if we transform $x$.

This is generally what we want from the laws of physics.

E.g. a Galilean transformation generally changes the exact values of coordinates, but not the form of the laws of physics themselves.

Lorentz covariance is the main context under which the word "covariant" appears, because we really don't want the form of the equations to change under Lorentz transforms, and "covariance" is often used as a synonym of "Lorentz covariance".

TODO some sources distinguish "invariant" from "covariant": invariant vs covariant.

Some sources distinguish "invariant" from "covariant" such that under some transformation (typically Lie group):TODO examples.

Bibliography:

Subgroup of the Poincaré group without translations. Therefore, in those, the spacetime origin is always fixed.

Or in other words, it is as if two observers had their space and time origins at the exact same place. However, their space axes may be rotated, and one may be at a relative speed to the other to create a Lorentz boost. Note however that if they are at relative speeds to one another, then their axes will immediately stop being at the same location in the next moment of time, so things are only valid infinitesimally in that case.

This group is made up of matrix multiplication alone, no need to add the offset vector: space rotations and Lorentz boost only spin around and bend things around the origin.

One definition: set of all 4x4 matrices that keep the Minkowski inner product, mentioned at Physics from Symmetry by Jakob Schwichtenberg (2015) page 63. This then implies:

Inkscape is a a good software for editing/creating SVG files.

Its functionality is fundamental for as a software for drawing geometry diagrams, as it is a good middle ground between algorithmic generation, and raster graphics.

At 1.0.2, its UI is a bit terrible:

And it crashes from time to time on Ubuntu 21.04. And it has some glaring bugs, e.g.:

But still, it is a very good initiative.

There's a tiny little crosshair that you can drag around to set the center of rotation.

And there's a button to make that crosshair snap: inkscape.org/forums/questions/can-a-pivotingtransfrom-crosshair-be-moved-and-made-to-snap-to-a-node-or-a-grid-point/#c14432