Online Batch Image Brightness Adjustment Tool

What Online Batch Image Brightness Adjustment Tool actually does

Batch brightness adjustment for up to 30 selected images. One Adjustment strength (%) numeric setting is shared by all files; it defaults to 25 and is bounded from -100 to 100. Positive values brighten, negative values darken and zero leaves RGB unchanged.

Checkable example

Verified examples: RGB(100,160,240) at amount 20 becomes RGB(151,211,255), so the blue highlight clips; at -20 it becomes RGB(49,109,189). This fixed channel offset is different from proportional darkening, white-blend lightening and exposure-stop scaling.

Controls, output and limits

For each pixel, the implementation adds 255*amount/100 to red, green and blue independently and then clamps and byte-rounds each result to 0..255. Alpha and image dimensions are retained by the canvas operation.

Worked batch use: load an underexposed product photo and a brighter outdoor photo, select amount 20 and Generate. Both receive the same +51 channel offset, but the outdoor highlights may clip sooner. Review every preview instead of assuming one setting suits the full batch.

Each input must have an image MIME type, be no larger than 25 MiB and decode to no more than 24,000,000 pixels. The selected batch is limited to 100 MiB and 40,000,000 decoded pixels; a selection over 30 files is rejected as a whole.

Every result is encoded as PNG and named from the source base name plus -brightness.png. Download all triggers separate downloads about 180 ms apart, not a ZIP. The tool does not preserve the original file format or offer an output-format selector.

Processing and previews occur locally in the browser. Generate must be pressed again after changing the amount. This is a global decoded-raster adjustment, not RAW recovery, automatic exposure, a subject mask or a local brush. Clipping cannot be undone reliably, so keep the originals.