Image Brightener
Brighten a dark photo, add contrast to a flat one, or fix a dull picture with auto levels. Brightness, contrast, exposure, gamma and saturation sliders, with a before/after view and a full-size download.
- 1Choose an image
- 2Adjust
- 3Download
1Choose an image
or drop an image here, or paste one with Ctrl/Cmd+V
Your image never leaves your device. The changes are made in your browser. We count visits and finished downloads (tool name only) with analytics that sets no cookies.
2Adjust
Before and after
The example image, changed with this tool. Middle: Brightness +15 and Gamma 1.30. Right: Contrast +40 and Saturation +30.
How to brighten an image
- Choose an image (JPG, PNG, WebP or GIF), or press Try with an example.
- Move the sliders. Brightness or Exposure makes the whole picture lighter; Gamma lightens the midtones and keeps black and white; Contrast spreads the darks and lights apart.
- For a dull or hazy photo, tick Auto levels first, then fine-tune.
- Compare with the before/after slider, or drag across the picture.
- Choose PNG or JPG and press Download. The download is made at full size with exactly the same settings.
What each control does
- Brightness adds the same amount to every value, so everything gets lighter (or darker) by the same step. Large amounts make the picture look washed out.
- Exposure multiplies every value, like opening the camera's aperture: +1 EV doubles the light, −1 EV halves it. Shadows stay dark, highlights reach white first.
- Gamma bends the middle of the curve. Above 1 it brightens midtones and shadows, below 1 it darkens them. Pure black and pure white do not move, so it is the gentlest way to brighten a dark photo.
- Contrast pushes values away from mid-grey (positive) or pulls them towards it (negative). At −100 the picture is flat grey.
- Saturation makes colors stronger or weaker. At −100 the picture is black and white.
- Auto levels finds how dark and how light each color channel really goes and stretches it to the full range. It often removes a color cast as well.
FAQ
How do I brighten a dark photo?
Choose the photo above and raise Gamma to about 1.3 to 1.6 first: it lightens the shadows and midtones without turning black into grey. If it is still dark, add some Exposure. Check it with the before/after slider, then press Download.
What is the exact math behind each control?
Each red, green and blue value v (0 to 255) is turned into x = v / 255, then these steps run in this order. After every step x is kept between 0 and 1.
- Auto levels (if ticked): x = (v − lo) / (hi − lo). For each channel, lo and hi are the values that cut off the darkest and brightest 0.5% of pixels, measured on the image.
- Exposure E: x = x × 2E.
- Brightness B: x = x + B / 100.
- Contrast C: x = (x − 0.5) × (1 + C / 100) + 0.5.
- Gamma g: x = x1/g.
- Saturation S: each channel c becomes Y + (c − Y) × (1 + S / 100), where Y = 0.2126 R + 0.7152 G + 0.0722 B (Rec. 709 luma).
The result is round(x × 255). Transparency (alpha) is not changed. For example, Brightness +20 turns a value of 100 into 100 + 51 = 151.
What is the difference between brightness and exposure?
Brightness adds: every value goes up by the same amount, so black becomes grey. Exposure multiplies: dark values change little and light values change a lot, so black stays black. Gamma sits between the two and changes the midtones most.
How do I increase the contrast of an image?
Move Contrast to the right. +30 to +50 suits most flat photos. If the picture looks faded or hazy, tick Auto levels first, because it stretches the real darkest and brightest parts to black and white before any other change.
Does it make the picture smaller or lower quality?
No. The download has the same width and height as your image unless you pick a smaller Size (very large images are worked on at 4096 px on the longest side). PNG keeps every pixel exactly; JPG is saved at quality 92.
Does it keep transparency?
Yes. Only red, green and blue are changed. Download a PNG to keep transparent parts; JPG has no transparency, so the picture is put on white.
Is it free? Is there a watermark?
It is free, with no sign-up and no watermark.
Does this tool upload my image?
No. The picture is read, changed and saved by your browser on your own device. Your image is never sent to a server. You can check: open your browser's developer tools, go to the Network tab, and use the tool. No request carries your image. The page counts visits and finished downloads (tool name only) with analytics that sets no cookies, and no file data is ever sent (see privacy).