Online Batch Image Duotone Effect Tool

What this tool actually does

Batch duotone mapping for up to 30 selected images. Two native color pickers are shared across the batch: shadows default to #111827 (RGB 17,24,39) and highlights to #22D3EE (RGB 34,211,238). Invert colors is off by default; there is no per-image override.

Checkable behavior

For each source pixel, weighted luminance q=(0.299R+0.587G+0.114B)/255 selects a linear position between the shadow and highlight colors. Invert replaces q with 1-q. Alpha and image dimensions remain unchanged.

Controls, output and limitations

With defaults, black maps to #111827 and white to #22D3EE. Verified example: RGB(100,150,200) maps to approximately RGB(26,127,149); with Invert enabled it maps to approximately RGB(25,108,128), after byte rounding.

Worked batch use: load a series of campaign photos, choose one dark brand color and one light accent, then Generate. All files use the same endpoints, while each pixel's luminance controls its mixture. Review every image because different original colors with equal luminance collapse to the same result color.

Each input must have an image MIME type, be at most 25 MB and decode to at most 24,000,000 pixels. The selected batch is capped at 100 MB and 40,000,000 decoded pixels; selecting more than 30 files rejects the whole selection.

Every result is encoded as PNG and named duotone-1.png, duotone-2.png and so on in batch order. Download Result starts separate downloads about 160 ms apart; it does not make a ZIP, retain source base names or offer another output format.

Processing is local in the browser and Generate must be pressed after control changes. This is a continuous luminance gradient between two colors, not a two-color threshold, indexed-palette reduction, spot-color separation, original-hue preservation or selective masking. Retain the originals.