Online Image Brighten Tool
Lighten an image by blending RGB channels toward white; preview and download one PNG locally. Processing takes place locally in your browser.
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What Online Image Brighten Tool actually does
Adjustment strength field defaults to 25 and displays -100 to 100. Positive amounts move channels toward white, zero leaves RGB unchanged, negative amounts move away from white and can clip shadows.
Checkable example
Formula per channel c: c+(255-c)*amount/100. Example RGB(100,160,240) at 20 becomes (131,179,243) after byte rounding. At 100 all RGB channels become white.
Controls, output and limits
Unlike brightness adjustment, the offset depends on the starting channel: dark channels move farther than bright ones. This is not shadow-detail reconstruction, exposure correction in stops, or a selective mask.
Browser-local single-image preview and download. Keep the source: lightening can wash out contrast. Batch processing and AI restoration are unavailable; export does not guarantee preservation of the original format.
Enter a finite number from -100 to 100 in the strength field; decimals are accepted, blank and out-of-range values are rejected. Each generation starts from the selected original. At -100, channel 240 becomes 225, not 0. Pixel bytes round to nearest, with exact halves going to even: RGB(80,120,200) at 30 becomes (132,160,216). Alpha is retained, but canvas decoding can affect transparent RGB. Export is one static PNG at the decoded pixel dimensions, without original metadata or animation guarantees. Maximum file size is 25 MiB (26214400 bytes), maximum pixels 24000000. Clear removes the source and result and disables download, keeping the strength value.
Processing takes place locally in your browser.