Duotone

Duotone replaces the color of an image with a two-color ramp: it measures each pixel's Rec. 709 luminance and looks that value up in a 256-entry table running from your shadow color at black to your highlight color at white. Six presets are built in — Cyanotype, Sepia, Noir, Acid, Ink and Ember — and moving either swatch turns the pair into a custom one. An intensity slider blends the mapping back toward the original image, and "Preserve highlights" lets anything brighter than luminance 200 run on to white instead of stopping flat at the highlight color.

How it works

  1. Drop your images Drag one or more files onto the drop area. The first one that decodes is what the live preview and the ramp strip speak for.
  2. Pick a preset or two colors Choose Cyanotype, Sepia, Noir, Acid, Ink or Ember, or set the shadow and highlight swatches yourself. Moving either swatch releases the preset.
  3. Set the intensity The intensity slider runs 0 to 100. At 100 none of the original color is left; at 0 the file comes out exactly as it went in, and the tool says so.
  4. Decide about the highlights Turn on "Preserve highlights" to let specular highlights fade toward white past luminance 200, rather than stopping at your highlight color.
  5. Process and download Pick Keep, PNG, WebP or JPEG, press Process, then Download. A batch comes back as file4edit-duotone.zip.

Questions

Does Duotone keep transparency?
The mapping never writes the alpha byte, so soft edges and transparent areas survive intact — a transparent pixel has no visible color to map. But if you write the result to a format with no alpha channel, such as JPEG, the transparent areas are filled with your shadow color, and the tool posts a notice naming the format before you process.
Why does my image come out as a flat block of color?
Because the two colors are too close in brightness. Duotone maps luminance along the ramp, so if the shadow and highlight colors are within 24 luminance points of each other there is almost no range to map into. The tool warns when that happens; pick a darker shadow or a lighter highlight.
Is the result the same every time?
Yes. Duotone builds a 256-entry lookup table from the two colors — index 0 is the shadow color exactly and index 255 is the highlight color exactly — and every pixel is remapped through that same table. Nothing is random, so the same image with the same settings always produces the same output.

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