ChannelMark6.8

A local-browser watermark tool with batch export, saved copyright settings, PNG copyright metadata, and an optional dual-axis mid-frequency ownership signature designed for better resistance to moderate JPEG compression. Visual text reveal and blind signature detection are separate features.

1 · Image and copyright name

Photograph

Select multiple photos for batch processing. Use a full-resolution original. Processing stays in this browser.

This exact name is encoded as a repeated tiled pattern.

⚙ Advanced watermark settings

Pixel-channel strength 2.5 / 255

Lower is more discreet; higher is easier to reveal but more likely to tint pixels.

Watermark rows 8

Choose 3–16 rows across the photo. Fewer rows make larger text. Each row repeats the complete copyright name across the full image width.

Embedding channel

Luminance changes all RGB channels together, reducing dependence on fragile blue/chroma information. Strong compression may still destroy the mark.

Compression-resistant signature

Adds a seeded, zero-mean 16×16 dual-axis spatial-frequency pattern. Detector uses your copyright name as a key; no original required. This is an experimental correlation watermark, not a guarantee.

Signature strength 3.5

Higher values improve recovery but can make fine texture more visible.

Settings are stored only in this browser on this device.

Batch export format

Individual mode prepares separate PNGs. On iPhone, use Share all PNGs; on desktop, download individually or try Download all.

Choose one or more images and enter a copyright name.

On iPhone, the export button opens the Share sheet when supported. Choose “Save Image” or “Save to Files”.

Copyright metadata · PNG iTXt + EXIF

⚙ Advanced metadata settings

Rights / portfolio URL (optional)

Preserve original camera and lens metadata

Copy supported EXIF fields from JPEG, PNG, or HEIF/HEIC sources into exported PNG. Proprietary MakerNotes and thumbnails are not copied.

Preserve GPS location (opt-in)

Off by default to protect photo locations. Enable only when you intend to share coordinates.

Metadata settings are saved in this browser only.

Metadata diagnostics will appear after you select a photo.

PNG exports include copyright iTXt and supported camera/lens EXIF (eXIf) from JPEG, PNG, or HEIF/HEIC originals. GPS is excluded unless explicitly enabled. Some formats and proprietary fields are unsupported.

2 · Reveal it

Reveal preset

High-pass subtracts a blurred luminance background to emphasize subtle local changes, but photo texture may still obscure the mark. Compare with original isolates the embedded signal exactly, and only works while the original image is available.

Reveal boost 8×

Preview-only amplification. This does not change the downloaded file.

The reveal preview amplifies small pixel changes so you can inspect the signature.

3 · Pattern detection

The detector correlates a name-derived mid-frequency signature with the image. It does not require the original, but it assumes the image dimensions and orientation are unchanged. It can be tested on a JPEG re-export. A score alone is not proof of ownership.

Optional: choose a copy to test

Important limitations

The reveal pattern is encoded into the selected pixel channel(s) using a repeated text mask. There is no separate transparent text layer.
Normal appearance is controlled by a small per-pixel channel delta. The reveal preset isolates that channel and amplifies its contrast.
The mid-frequency signature is repeated over many 16×16 blocks and tested by correlation. It is more compression-tolerant in principle, but not cryptographically secure and can produce false positives.
JPEG recompression may preserve the signature, but resizing, cropping, rotation, aggressive denoising, or platform-specific processing may defeat it. The detector expects the original pixel grid and dimensions.

Important: This is an experimental visual watermark, not a secure or tamper-proof forensic standard. A low-strength channel mark can be removed, and aggressive reveal adjustments also amplify image noise and texture. Keep original RAW files, unwatermarked masters, dated exports, and a separate ownership record.