Histogram Equalization is a technique that redistributes pixel intensity values so that the resulting histogram is approximately uniform (flat). This effectively stretches the contrast in areas where it's most needed, making details more visible in dark or washed-out regions. It works by computing the cumulative distribution function (CDF) of pixel intensities and mapping original values to new ones based on the CDF.

CLAHE (Contrast Limited Adaptive Histogram Equalization) improves upon standard HE by operating on small regions (tiles) of the image rather than the entire image at once. Key advantages:

• Local adaptation: Each tile gets its own equalization, preserving local contrast better.
• Contrast limiting: A clip limit prevents over-amplification of noise in homogeneous areas.
• Smoother results: Bilinear interpolation between adjacent tiles eliminates block boundaries.

CLAHE is especially useful for images with both very dark and very bright regions, where global HE would fail.

This tool is ideal for:

• Underexposed photos — bring out hidden shadow details
• Hazy or foggy images — improve clarity and definition
• Low-contrast scans — enhance documents, X-rays, or medical imagery
• Backlit subjects — recover details lost in silhouette
• Satellite or scientific imagery — reveal subtle intensity variations

Note: For already well-exposed images, HE may produce unnatural results. Use the Strength slider to blend and find a natural balance.

The Strength slider (0–100%) controls how much of the equalized result is blended with the original image:

• 0% = Original image (no enhancement)
• 100% = Full histogram equalization
• 50–80% = Sweet spot for most photos — visible improvement without looking artificial

In CLAHE mode, the strength also affects the clip limit internally, giving you nuanced control over local contrast amplification.

Yes, completely. All image processing happens entirely within your browser using JavaScript and the HTML5 Canvas API. Your images are never uploaded to any server. The tool works offline once the page is loaded. Your privacy is fully protected — no data leaves your device.

This tool uses luminance-preserving equalization. We compute the brightness (luminance) of each pixel using the weighted formula Y = 0.299R + 0.587G + 0.114B, equalize only the luminance channel, then scale RGB values proportionally. This preserves the original color hue and saturation, avoiding the unnatural color shifts that can occur when equalizing R, G, and B channels independently.