Function chroma_key_definition 

pub fn chroma_key_definition() -> EffectDef

Returns the data-only definition of the built-in chroma-key effect.

key_color is compared with each pixel’s straight color as the renderer stores it: sRGB-encoded, not linear light. Pick the key as a color picker shows the screen. With distance_mode at rgb a pixel within threshold of the key in that RGB space is removed, softness wide edges are partly transparent and spill_suppression desaturates them; chroma compares only the chroma plane, so a key survives shadows on a screen.