Does any of the original colour survive?

No. Each pixel keeps only its brightness, which is then mapped between your two colours. Original hues are discarded entirely.

Why does the image look smaller than the file I uploaded?

It is scaled to a maximum of 800 pixels on the longest side before processing, so the canvas is a working preview. The colour choice transfers unchanged to a full-resolution edit.

How do I download the duotone image?

There is no download button. Right-click the canvas and save the image, or note the two colours and apply them at full resolution in an image editor.

Which colour should be the shadow?

Usually the darker, more muted of the two, since it stands in for the image's dark tones. Swapping them inverts the effect and is a quick way to produce a negative-feeling variant.

What happens if the two colours are close in brightness?

The map flattens: the image's tonal detail lives entirely in the distance between the shadow and the highlight colour, so a pair of near-matches collapses the picture towards one tone. Keeping one end clearly darker than the other is what gives the effect its depth.

Duotone Generator

Drop an image here, or click to upload

PNG, JPG, WebP, GIF

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The duotone generator maps an image onto a two-color gradient, replacing every pixel with a blend between a shadow colour and a highlight colour chosen by its brightness.

What is Duotone Generator?

The duotone generator takes an image and two colours — labelled Shadow and Highlight — and rebuilds the image from nothing but those two values. Upload through the dropzone and the canvas appears beside the controls; change either colour and the image is redrawn immediately. Replace image clears the file so another can be loaded.

The transformation is a gradient map, which is the defining characteristic of a duotone effect. For each pixel the tool first computes a single brightness value from the original colour, then uses that brightness as a position along a line drawn between the shadow colour and the highlight colour. Bright pixels land near the highlight, dark pixels near the shadow, and everything in between is interpolated. Nothing of the original hue survives — two photographs of the same scene lit differently will come out with the same colours if their brightness patterns match, which is why a duotone image always looks as though it was made from two inks.

The luminance figure uses the Rec.601 weights — roughly 0.299 red, 0.587 green and 0.114 blue — the same weighting older video systems used.
Green therefore contributes noticeably more to perceived brightness than blue, so two colours of identical intensity on screen can sit at different points on the gradient.
It is a good general approximation, and the one most image tooling has historically used.

The image is also scaled down to a maximum of eight hundred pixels on its longest side before it is processed. That keeps the effect responsive while dragging a colour picker, and it means the canvas you see is a working preview rather than a full-resolution render. For picking colours that is the right trade — the effect is a global mapping, so the palette decision looks the same at any size — but it does mean the canvas is not what you would want to ship to print.

Where the tool fits is quick art direction, or as a way to convert image to duotone for a set of assets that need a house style. A two color image effect like this is a reliable way to make a set of mismatched photographs feel like one family: apply the same shadow and highlight to all of them and the differences in lighting and colour cast disappear. It also works as a background treatment, pushing an image back so foreground text can sit on top without competing. Choosing the two colours is the whole craft here — a light highlight and a dark shadow give contrast, while two mid-tones give a flat, poster-like result that suits a stylised look.

Be clear about the output route, because there is none built in. The result is drawn onto a canvas and there is no download button, so the way to keep it is to right-click the canvas and save the image, or capture it. Combined with the eight-hundred-pixel working size, that makes this a tool for exploring and deciding, after which the same two colours can be applied at full resolution in an image editor.

How to use Duotone Generator

Drop an image onto the upload area.
Set the Shadow colour for the darkest tones in the image.
Set the Highlight colour for the brightest tones and watch the canvas redraw.
Right-click the canvas to save the result, or reuse the same two colours at full resolution elsewhere.

When to use Duotone Generator vs related tools

Use this when a set of images needs a consistent look, or when a photograph has to recede behind foreground content. Use the image recolour tool when you want to change the hue of an image while keeping its tonal structure similar to the original. When the hues should shift without collapsing to two colours, the image recolor tool keeps the tonal structure and moves the hue instead, and a single tint over the whole frame is what the overlay color generator previews.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.