Hydra color transforms multiply, shift, or key the RGBA channels of a texture

Color transforms modify the RGBA values of each pixel without moving geometry. .brightness(amount) shifts luminance; .color(r,g,b,a) multiplies each channel independently (negative values invert that channel); .invert(amount) inverts all channels, with amount 0–1 blending between original and inverted; .hue(hue) rotates the hue wheel (0.5 outputs complementary colors); .luma(threshold, tolerance) keys out dark regions, removing pixels below the luminance threshold — useful for compositing. These transforms are purely per-pixel: they do not affect neighboring pixels or geometry, so they compose cleanly with geometry transforms and blending.

Examples

osc(30).color(1, 0, 0.5).hue(0.3).out()
noise().luma(0.4, 0.05).invert().out()

Assessment

What does .hue(0.5) do to a color? Given a patch that should remove dark areas, which color transform and parameter achieves it? Write a patch using three color transforms.