zBase indeed does provide 2x scale GUI icons. IMHO that's something which should be changed so that it also provides the 1x size icons. Maybe Zephyris can provide us with those; then I'll be happy to change itjuzza1 wrote:If I understood you correctly: You want to reduce the size of the 2x sized GUI icons (not to be confused with the NewGRF "OpenGFX BigGUI") included with zBase to that of the original. If so, there is no simple way to do this, because as you said, the GUI is hard coded into zBase, and base sets do not support parameters. The easiest way to achieve something similar to this is to use OpenGFX BigGUI with zBase and, and set its size to 1.5x from the NewGRF parameters. 1x scaling uses the default graphics defined by the current base set, which means you will still get the 2x sized GUI of zBase. This behaviour isn't really what you would expect, and as such, it's marked as an issue at the OpenGFX BigGUI devzone (http://dev.openttdcoop.org/issues/3599).
However, even when you want to reduce the size of your GUI icons now, you can use OpenGFX+ BigGUI and set the desired GUI size to 1x (or 1.5x) instead of 2x.
EDIT: and I realize that Juzza mostly wrote that already