Duotone effect
Shadows in one colour, highlights in another.
Drop files here
or click to choose from your deviceAccepted: JPG, JPEG, PNG, WEBP, AVIF, GIF, BMP, HEIC, HEIF
Up to 3 files per runUp to 20 MB per file5 runs per dayRemove limits with Pro✓ Works offline
Your files stay on your device
This tool runs entirely in your browser. Nothing is uploaded, nothing is stored, and you can even turn off your internet connection before you start.
Example
Example: a gig photo in purple and orange for an A3 poster
A pub band wants its gig photo on an A3 poster in two colours: gig.jpg from a mirrorless camera, 8160 × 6120 pixels (about 50 MP). The singer stands in a spotlight in front of a black backdrop, with stage haze behind, a sunburst guitar and a chrome mic stand. Settings: Colours Purple and orange, Contrast High, Save as PNG.
- Each pixel’s brightness is red × 0.299 + green × 0.587 + blue × 0.114, from 0 to 255: backdrop 17, jacket 43, guitar 89, haze 116, skin in the stage light 165, mic stand 191, glare 250.
- High first stretches the range: the darkest 0.5% (backdrop, 17) becomes #3b0f6b, the brightest 0.5% #ffa64d. The glare is only 0.3%, so the mic stand (191) marks the top and turns pure orange.
- Then an S-curve: the jacket drops to #44166a, almost the shadow colour, the guitar to #7e4361, and the skin rises to #f69f4e.
- The photo is over 16 megapixels, so it is reduced to 4618 × 3464 (16.0 MP) and saved as gig-duotone.png — about 280 dpi across the 420 mm of an A3 sheet.
| Part of the photo | Colour (R, G, B) | Brightness | Low | Normal | High |
|---|---|---|---|---|---|
| Black backdrop | 18, 16, 22 | 17 | #481969 | #3b0f6b | #3b0f6b |
| Dark jacket | 45, 40, 50 | 43 | #5c2866 | #582667 | #44166a |
| Sunburst guitar | 150, 70, 30 | 89 | #7f4461 | #8c4d5f | #7e4361 |
| Stage haze | 120, 110, 140 | 116 | #94545d | #ab655a | #b66e58 |
| Skin in the spotlight | 210, 150, 120 | 165 | #ba7158 | #e28f51 | #f69f4e |
| Chrome mic stand | 190, 190, 195 | 191 | #ce8055 | #ffa64d | #ffa64d |
| Spotlight glare | 255, 250, 240 | 250 | #fba34e | #ffa64d | #ffa64d |
A two-colour poster: the backdrop solid deep purple, the singer and the haze glowing orange. At Low the backdrop would stay a lifted purple (#481969) and even the glare would not quite reach full orange; High gives the deepest shadows for print, at the cost of the mic stand’s detail.
How it works
- Add one or more photos.
- Pick a pair of colours, or choose My own colours and set the shadow and highlight colours; raise the contrast for a bolder poster look.
- Select Make it duotone and download the picture.
Frequently asked questions
- What is a duotone?
- A picture printed in two inks. Here the photo’s brightness decides the colour: the darkest parts take the shadow colour, the lightest the highlight colour, and everything in between a blend of the two. It is a quick way to put photos in a poster’s or a brand’s colours.
- What does the contrast setting do?
- Low maps the photo’s brightness as it is. Normal first stretches the photo’s own range, so its darkest part reaches the shadow colour and its lightest the highlight colour. High adds a curve on top, for deeper shadows and brighter highlights.
- Does it keep transparency?
- Yes. Transparent areas stay transparent in PNG and WebP; a JPG puts them on white. The photo keeps its size, up to 16 megapixels.
- Is this the same as a gradient map?
- Yes, a two-colour one. Each pixel’s brightness (0.299 × red + 0.587 × green + 0.114 × blue) picks a point on a straight blend from the shadow colour to the highlight colour. There are only the two colours, with no extra stops in between; Normal and High first stretch or curve the brightness.
- Why did two different colours turn into the same colour?
- Only brightness counts. A red and a blue of about the same brightness land on the same point of the blend, so a red sign on a blue wall can disappear. Pick photos where what matters is lighter or darker than what is around it, or raise the contrast.
- Is my photo uploaded, and what are the free limits?
- No. The duotone is made in your browser, so the photo never leaves your device, and there is no watermark. The free plan allows 3 photos of up to 20 MB per run and 5 runs a day; Pro removes these limits.