Show the Pictures

[starturtle]

The current program only runs silently in a shell.
There should be a way to display the files before and after conversion.
For that purpose, a rudimentary IO is missing.

First layout: Three rows with three (or two, resp.) entries each

• file chooser launcher, row input, column input (order not fixed)
• before and after canvas panels
• "convert" and "store" buttons

GUI framework not set yet.

[starturtle]

Timing is not that good yet (first store to file, then show file), but essentially, done.