Image Contrast Adjuster 🌗
Adjust contrast of images. Increase or decrease contrast with a slider.
Click to browse or drop an image here
JPG, PNG, WebPAbout the Image Contrast Adjuster
The Image Contrast Adjuster runs entirely in your browser. Drop or select an image, drag the Contrast slider between −100 and +100, and click Apply. The tool uses the standard contrast formula: a factor of (259 × (contrast + 255)) / (255 × (259 − contrast)) is computed, then each channel is transformed with factor × (value − 128) + 128. Positive values push lights lighter and darks darker; negative values flatten the image toward mid-gray. Download the result as a PNG. Nothing is uploaded to a server — all processing happens locally with JavaScript on your device.
How to use the adjuster
- Click the drop zone or drop an image file onto it.
- Drag the Contrast slider — positive to strengthen, negative to soften.
- Click Apply to render the effect onto the image.
- Click Download to save the result, Reset to restore the original, or Clear to start over.
Frequently asked questions
What does the contrast value mean? 0 leaves the image unchanged. Positive values up to +100 increase the difference between light and dark areas; negative values down to −100 reduce it.
What is the output format? The download is a PNG file. This preserves detail and avoids compression artifacts.
Does this tool upload my images? No. All processing happens locally in your browser. Your image never leaves your device.
Can I apply the effect multiple times? Yes. Each Apply works on the current canvas, so successive clicks compound the effect. Use Reset to return to the original.