image/texture inversion-negative

Is there a fast (hardware) method to do this?

I.e. a subtractive blend rather than additive blend. For such a simple operation you'd think you could do it on the GPU.

Anyone know if it's possible to do this in b3d?

You would have to code it yourself for standard Blitz3D (ie. a bit slow). You could always use a DLL (FastImage, FastExt or other?).

As beaker suggests, try the fastextend lib. It includes many more blend modes than standard blitz3d. It may have what you need. Try posting in the userlib section of the blitz3d forum, referencing fastextend lib. The author is usually around.

Thanks both - i'll check out those libs