Here is sample brush pipe file. Load in Gimp, export as a GIH:
BrushPipe.xcf (Size: 2.35 KB / Downloads: 384)
PS: rereading your post, it is possible that in addition to being gayscale, the layers should have no alpha channel. There should be no transparency if you want a "cameleon" brush, tranparency is determined by the white.
- Spacing: 100
- Cells: 3
- Dimension 1
- Ranks: 3, incremental
BrushPipe.xcf (Size: 2.35 KB / Downloads: 384)
PS: rereading your post, it is possible that in addition to being gayscale, the layers should have no alpha channel. There should be no transparency if you want a "cameleon" brush, tranparency is determined by the white.