Is there any dedicated test core like those under Utility that will generate video test patterns? I'm particularly looking for RGBW gradients for use on HDMI. I see the 240p Test Suite can serve this purpose but I am interested in testing the native default output on HDMI outside of any particular core. This came up in trying to tune the HDR settings.
Could this possibly be done in Linux (via the script mechanism maybe) rather than with a core? Would it be hard to make a core that does this?