Image Brightness/Contrast

The Image Brightness and Contrast Adjuster lets you fix exposure issues in photos directly in your browser. Dark photos too dim? Brighten them. Flat images looking washed out? Add contrast. Old photos lacking punch? Boost both brightness and contrast. Real-time preview shows changes immediately so you can dial in the right settings by eye. No upload, no account, no install — just a browser-based quick fix for common photo problems.

Brightness adjusts the overall lightness of the image (shift all values up or down). Contrast stretches or compresses the range between light and dark pixels. Both are implemented with simple per-pixel math using the Canvas API. Quality is preserved (lossless operation except for JPEG re-encoding). Works with JPG, PNG, WebP, GIF, and BMP formats. For more sophisticated photo editing (curves, selective adjustments, shadow/highlight recovery), use dedicated software; this tool handles the common 80% case quickly and for free.

Brightness adjustment:

new_value = old_value + offset

Offset ranges from -255 (all black) to +255 (all white). 0 means no change. Values are clamped to 0-255 at output.

Contrast adjustment:

new_value = (old_value - 128) × factor + 128

Factor > 1 increases contrast; factor < 1 decreases. A factor of 2.0 doubles the distance from middle gray (128); a factor of 0.5 halves it. Values clamp to 0-255.

Combined:

new_value = ((old_value - 128) × contrast + 128) + brightness

Per-channel: applied to R, G, B independently. Alpha unchanged.

Brightness slider typical range: -100 to +100 (mapping to -100 to +100 offset).
Contrast slider: -100 to +100 (mapping to factor 0 to 2.0, where 0% = factor 1.0).

Clipping behavior: values above 255 become 255 (white highlight); below 0 become 0 (black shadow). High brightness or contrast can cause clipping that loses detail in shadows or highlights. The tool shows a warning when significant clipping occurs.

Gamma correction: for more perceptually accurate adjustments, some tools apply brightness in linear light space rather than gamma-encoded sRGB. The difference is subtle but matters for professional work. This tool applies in sRGB directly (standard for most quick-adjust tools).

Histogram: sophisticated tools show a histogram indicating pixel distribution. Brightness shifts the histogram left/right; contrast stretches/compresses it. Clipping shows as spikes at the 0 or 255 end.

Exposure vs brightness: they\u2019re related but different. True exposure adjustment works in linear light space and simulates the effect of more or less light hitting the sensor (multiplicative). Brightness as implemented here is additive in sRGB space, which is simpler but less photometrically accurate.

Performance: per-pixel O(n) operation, hardware-accelerated by Canvas 2D. Multi-megapixel images adjust in under a second.

Compared to Photoshop or Lightroom, this tool is simpler and faster for basic brightness/contrast tweaks. Editors offer much more control; this tool is for quick fixes.

Compared to phone photo apps, this tool preserves original quality better (no additional compression beyond your chosen format).

Compared to CSS filters in the browser, this tool saves the adjusted image as a file. CSS filters only apply in display; this tool creates the adjusted output.