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Utility

Online Image Watermark Tool - Batch ID Photo Anti-Theft Generator

Runs locally · no upload

Add text or logo watermarks to images locally in your browser. Supports 9-grid positioning, diagonal tiling, batch processing and PNG/JPG/WebP export. Perfect for ID cards and business licenses. Zero upload for full privacy.

Overview

Batch-watermark images locally in your browser with text or a logo. 9-grid anchor and diagonal tiling make it ideal for protecting ID cards, bank cards and business licenses from theft. All processing happens in Canvas on your device - nothing is uploaded. Up to 20 files per batch, 20 MB each.

How to use

  1. Pick a "preset scenario" (ID card anti-theft, business license, etc.) or stay with Custom
  2. Click "Image files" and select up to 20 JPG / PNG / WebP images
  3. Choose watermark type (text / logo / text+logo) and fill in the content
  4. Tweak font size, color, opacity, rotation, and pick one of 9 anchors or Tile mode
  5. Click "Add watermark"; download each result from the list on the right

Formula

Anchor watermark coordinate: x = anchorX + edgeMargin, y = anchorY + edgeMargin (anchor = 9-grid position). Tile loop: for i in 0..ceil(W/(tileW+gapX)), for j in 0..ceil(H/(tileH+gapY)). Rotation: ctx.translate(cx,cy) → ctx.rotate(rotation × π / 180) → draw → ctx.restore(). Opacity: ctx.globalAlpha = opacity / 100. Logo scale: width = image.width × logoSizePercent / 100; height scales proportionally.

Common scenarios

ID card copy anti-theft

Pick the ID-card preset, enter a purpose line like 'For XX business only', diagonal -30 degrees at 40% opacity, tiled. Even if the copy leaks, the visible watermark limits where it can be abused for fake account or company registration.

Batch business-license watermarking

Bidding, account opening and similar flows often require a business-license copy. Pick the Business-license preset, enter your short name and purpose, batch-watermark 10 archive scans, then send each copy to different partners.

Photography social post

Pick the Photo-tile preset (or set font color 80% white with a light shadow), tile diagonal signature across the image to prevent unauthorized reuse, and export as WebP for smaller size without quality loss.

FAQ

Will my images be uploaded? Is ID-card watermarking safe?

No. Everything runs locally in your browser. Files are read via FileReader into memory, rendered with Canvas, and exported back to your disk - no fetch or XHR upload anywhere. Closing the tab clears all data. This is among the safest ways to watermark ID cards, bank cards and business licenses.

How do I add anti-theft watermarks to ID cards or bank cards?

Pick the ID-card or Business-license preset and make the text explicit about purpose, e.g. 'For XX bank account opening only'. Set position to Tile, rotate -25 to -30 degrees, opacity 30-50%. The result is readable yet covers key fields, and the purpose text is legal evidence if misuse occurs.

How many images can be processed in a batch?

Up to 20 files per batch with 20 MB per file, to avoid exhausting browser memory. If you upload more than 20, the tool keeps the first 20 and warns about the rest in the top-right area. For very large batches, process in groups and zip the outputs with your OS.

What if Chinese text shows up as blank boxes?

That usually means the chosen font lacks Chinese glyphs. Switch Font Family to Microsoft YaHei or PingFang SC so the OS-installed Chinese font is used. If still broken, ensure your system has Chinese font packs installed. Whatever Canvas renders is what the exported file keeps.

Can I combine text and logo watermarks?

Yes. Choose 'Text + Logo', upload a logo (transparent PNG recommended). Text renders below the logo and they share rotation / opacity / position. If you need different angles for each, process twice (logo first, then run the exported file through the tool again for text).

PNG, JPG or WebP: which export format should I pick?

Pick PNG when transparency matters (logos, screenshots). For photos and IDs choose JPG or WebP (WebP is usually ~25% smaller than JPG). When source is PNG/WebP but output is JPG, the tool auto-fills a white background to avoid black artifacts. For ID anti-theft, JPG (best compatibility) or WebP (smallest) is recommended.

Will my settings persist next time?

Yes. Key settings (text, font size, color, opacity, position, rotation, export format) are saved to localStorage and restored on next visit. If localStorage is disabled (e.g. incognito mode), the tool falls back to defaults without throwing any errors.

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