Gradient map
A color lookup that replaces shadows, midtones, and highlights with matching colors from a chosen gradient.
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What it is
A gradient map replaces each pixel according to its luminance. Black samples the left end of a chosen gradient, white samples the right end, and every gray value takes the color at the matching position between them.
Use it to build duotones, colorize grayscale art, or give shadows, midtones, and highlights a controlled palette in one pass. Photoshop has a Gradient Map adjustment; shaders perform the same lookup with a one-dimensional color ramp.
Gotcha: this is different from placing a gradient over the image. The source brightness chooses the output color, so crowded stops can flatten contrast or create abrupt posterized bands. Space the stops with the image's tonal range in mind.
Ask AI for it
Apply a gradient map driven by source luminance: map black to deep navy, mid-gray to rust orange, and white to pale cream, interpolating through one-dimensional linear RGB color stops. Preserve clear tonal separation and do not place a positional gradient over the image.