Duotone

Applies a duotone effect—a gradient with two different colors as its endpoints—to the image.

To achieve this effect, the image is first converted to greyscale. Two colors, usually contrasting, are then mapped to that gradient. In duotone={color1},{color2}, the first color is mapped to the darker parts of the image, and the second to the lighter parts. If you were to set a light color as color1 and a dark color as color2, you would create a duotone with a photo negative effect.

The duotone parameter accepts colors, expressed as either color keywords or 3- (RGB) or 6-digit (RRGGBB) hexadecimal color values. The opacity of the duotone effect can also be set separately using the parameter duotone-alpha. The default value is 100, which makes the duotone fully opaque. To blend the duotone with the original image, set a lower duotone-alpha value.