Transparent Image Batch Trimmer

How to use Transparent Image Batch Trimmer

Trim a supplied image batch to alpha-threshold content bounds and export actual padded PNG copies with source-coordinate witnesses. Choose an opacity cutoff and transparent padding. A real ZIP contains each separate trimmed PNG and a manifest; originals and their dimensions are recorded without overwriting files.

1. Provide static images to trim, minimum visible alpha, inclusive, transparent padding in pixels.
2. Choose the supported mode and run the tool. Review its assumptions and any reported errors.
3. Copy the result or download a separate output; reset to clear the current form.

Good to know

• 1–8 files, 8 MiB each, 24 MiB combined, 1,000,000 pixels and 2,048 pixels per side each, with 4,000,000 source pixels combined. Every file is structurally checked before any native decoding. Static non-animated PNG, baseline JPEG or simple VP8/VP8L WebP only. Structural/CRC preflight precedes native decoding. APNG, progressive JPEG, extended/animated WebP, compressed PNG metadata, SVG/GIF and orientation changes that disagree with the header are refused.
• Alpha is browser-provided 8-bit opacity. The bounding rectangle includes every pixel whose alpha is greater than or equal to an integer cutoff 1–255. Padding is an integer 0–128 transparent pixels added outside that cropped rectangle; it is not a background-color detector, subject crop or matte removal.
• Every output is at most 2,000,000 pixels and 2,048 per side; accumulated output dimensions are capped at 4,000,000 pixels before each canvas is resized. PNG bytes total at most 16 MiB, ZIP at most 17 MiB. Output names are generated image-001.png etc.; supplied names are manifest text only, never archive paths.
• For an empty mask, either fail the whole batch or generate one transparent content pixel plus the requested surrounding padding. No source pixel is claimed as its content. A cutoff of 255 can exclude partially transparent edge detail; inspect the rectangle witnesses. JPEG starts fully opaque and generally will not trim.
• Bounds run in a same-origin module Worker after preparation (10 seconds) with a separate 2-second calculation deadline per image. Native decode waits up to 10 seconds and PNG encoding up to 5 seconds; codec work cannot be forcibly aborted. Every bitmap/canvas is released, including failures and late decoded results.
• Browser color conversion, premultiplication and PNG encoding can change hidden RGB or metadata. This creates new pixel artifacts, not lossless source-byte edits. The tool does not align animation frames, preserve original registration or promise archival color fidelity.
• Structured text output is limited to 500,000 characters. Reduce the supplied source when that separate output budget is exceeded.
• Inputs are processed on this device and are not automatically saved or uploaded.