Online Batch Image Glow Effect Tool

What this tool actually does

Batch glow accepts up to 30 selected images and applies one shared Intensity and Kernel size to every loaded image. Intensity is 0-100% with step 0.01 and defaults to 25%; Kernel size defaults to 5 and is constrained to odd sizes from 3 through 13, with no per-image override or automatic preview.

Checkable behavior

The browser first computes a square box blur by averaging every RGB channel over the selected 3x3, 5x5, 7x7, 9x9, 11x11 or 13x13 neighborhood, repeating the nearest source pixel beyond image edges. It then adds amount/100 of that blurred RGB to the original RGB and clamps each output byte to 0-255.

Controls, output and limitations

Intensity 0% returns the original RGB, 25% adds one quarter of the blurred value, and 100% adds the full blurred value. This is an additive bright glow, not a blend that replaces the source with blur. Alpha and image dimensions remain unchanged.

Verified example: in a 3x3 black image with a grayscale center pixel of 90, the 3x3 box blur at the center is 10. The center output is 90 at 0% Intensity, approximately 92 at 25%, and 100 at 100%, with the original alpha retained.

Larger kernels spread bright areas over a wider neighborhood but do not expose a separate radius, threshold, color or blend mode. Additive output can clip bright channels and does not restore clipped detail; dark content creates little visible glow.

Each input must have an image MIME type, be at most 25 MiB and decode to no more than 24,000,000 pixels. The selected batch is capped at 100 MiB and 40,000,000 decoded pixels; selecting more than 30 files rejects the whole batch.

Generate creates one browser preview per loaded image. Every result is PNG named from the source base name plus -glow.png; Download all starts separate downloads about 180 ms apart, not a ZIP. Processing is local and is not bloom with a luminance threshold, colored neon, HDR, AI relighting or layer-based editing.