The first step of most multi-channel pipelines is to peel the channels apart. The Extract channelLoading... engine grabs one named or indexed channel as a grayscale imageLoading... you can feed into the rest of the pipeline. The Extract strongest channelLoading... variant picks the channel with the highest signal at each pixel — useful for combined visualizations but rarely for quantitative analysis.
Going the other direction: Set channels to RGBLoading... bundles three grayscale channels into an RGB image for display. Swap channelsLoading... reorders them. None of these change the underlying intensity data; they're channel arithmetic.
For RGB color imagesLoading..., the three channels aren't independent — they encode color as a trichromatic representation, and converting to a different color spaceLoading... reshuffles the channels in nonlinear ways. For fluorescence, channels generally are independent: each fluorophore reports a different molecular species, and the analysis treats them separately.