Darken a photo or lighten it
Make a whole photo darker, or lighter, with one slider. Add a caption on top and see at once whether it has become readable.
Local browser processing · No upload · No account required
Choose a photo to start. Text boxes and layers are drawn on your device.
How to darken an image
- Choose a photo. The page opens with Darken / lighten at minus 40, so the picture is already darker.
- Drag the slider left to darken further and right to lighten. At minus 100 the photo is black; at 100 it is white.
- Press Add text box if you want a caption, and use the contrast line to decide how dark the photo has to be.
- Press Save image. The file keeps the pixel size of the original.
How dark is dark enough for a white caption?
People search for ways to darken a photo mostly because something has to be read on top of it: a title, a date, a name. So I asked a plain question about my Lake Jasna photo. How far must I darken it before a white caption in the sky is readable?
I moved the slider in steps and let the tool measure white bold letters in the top left corner. Because the slider simply mixes black into every pixel, the answer is a table rather than a feeling. I also saved a JPEG at each step, because I wanted to know what darkening does to the file.
Lake Jasna at five settings of the slider
| Darken / lighten | Contrast of the white caption, worst / average | Saved JPEG |
|---|---|---|
| 0 (unchanged) | 1.1 / 1.3 | 421.9 KB |
| −20 | 1.8 / 2.1 | 393.3 KB |
| −40 | 3.1 / 3.7 | 338.1 KB |
| −60 | 6.2 / 7.0 | 276.6 KB |
| +40 (lighter) | 1.1 / 1.2 | 334.9 KB |
The sky only became readable at minus 60, and by then the whole lake was dim. Lightening made the caption worse, as expected. Both directions made the JPEG smaller, because a flatter picture has less detail to store; the photo saved without any change is 421.9 KB.
Darken the part that matters, not the whole picture
Minus 60 on the whole photo is a heavy price for a caption in one corner. When the text sits near an edge, a gradient from that edge reaches 4.5 and leaves the rest alone: on the same sky, a black gradient from the top at 60 % opacity over 45 % of the height gave 5.6 at the worst spot and 6.6 on average. That is the same readability as the slider at minus 60, with most of the lake untouched.
The main page has the gradient, and the box behind the text. Use this page when the whole mood of the picture should change, such as a dark background image for a slide or a banner.
Lighten for dark text
The slider works in both directions because dark text on a pale picture is just as common. Set the text colour to black, drag the slider to the right, and the contrast line measures black letters against the lightened pixels. Past about 60 the photo turns into a ghost image of itself, which can be exactly right for a printed invitation and wrong for a travel photo.
Tips for darkening a photo
- Change the slider in steps of 10 and stop as soon as the contrast line says Readable.
- For a caption near one edge, a gradient from that edge keeps more of the photo bright than the slider does.
- Darkening a photo and then saving a JPEG gives a smaller file than the original, which helps for uploads with a limit.
- Use the Lighten side with black text, and check the contrast line again after changing the colour.
Privacy
Your photo never leaves your device. Opening, drawing and saving all happen in your browser, and the fonts are served from this site. Nothing is uploaded and no account is needed.
Frequently asked questions
How do I darken an image online for free?
Choose your photo above and drag Darken / lighten to the left. The preview changes as you move it. Press Save image to download the darker file without a watermark and without creating an account.
Can I darken only the background of a photo?
This page darkens the whole picture. To darken one edge or corner, use the gradient on the main page, which fades from the side you choose. It does not cut out a subject from its background.
Does darkening a photo reduce its quality?
The pixel size stays the same. The darker picture is saved again as a JPEG, PNG or WebP, and for my Lake Jasna photo the JPEG at minus 40 came out 338.1 KB against 421.9 KB unchanged.
Can I lighten a photo with the same tool?
Yes. Drag the slider to the right instead. It mixes white into every pixel, so at 100 the photo is white. Lightening is useful behind dark text, and the contrast line measures it too.
How do I darken an image with CSS instead?
A web page can lay a semi-transparent black layer over the picture. This tool does the same thing inside the file itself, so the darker version also works in an email, a slide or a social post.
Related tools and guides
- Add text to your photo and keep it readable: Put captions on a photo with a gradient, tint or box behind them and a live contrast check.
- Give a photo a colour tint: Wash a photo in one colour, from a hint of warmth to a strong blue. Choose the colour and the strength, then save the result on your device.
- Lay a transparent colour over your photo: Cover a photo with one transparent colour. Choose the colour and how strong it is, add text if you want, and save the result at its original size.
- Image Resizer: Resize images by pixels, percentage or longest side.
- Image Cropper: Crop images to exact ratios or popular preset sizes.
- Put your photos together in one image: Join photos side by side, stacked or in a grid, with adjustable gaps and borders.
- Lake Jasna, Slovenia: My Photography and Visitor Guide: Where I took the lake photo with the pale sky.