InkStudio: 100% Client-Side Signature, Red Seal & Calligraphy Extraction Engine
InkStudio is a 100% browser-based handwritten signature, crimson company seal, and brush calligraphy transparent alpha extraction and SVG vectorization studio powered by an 81 KB zero-dependency Rust + WebAssembly engine over HTTPS with 0 bytes of documents uploaded to any server.
InkStudio unifies 4 specialized extraction modes across 4 languages (Simplified Chinese, Traditional Chinese, English, and Japanese) with localStorage persistence: O(1) 2D integral-image dual-scale illumination shadow stripping, Beer-Lambert continuous optical density alpha matting, directional morphological inpainting for red seals stamped over black contract text, notebook ruled/grid line removal, Felzenszwalb O(N) exact 2D Euclidean Signed Distance Field (SDF) stroke weight morphing (-2.5 px to +4.5 px), and one-click quadratic Bézier SVG vectorization.
How InkStudio Extracts & Vectorizes Signatures and Seals in 3 Steps
InkStudio Step 1 (Load Photo or Test 4 Built-in Samples): Drop any smartphone photo of a signature, stamped contract, or calligraphy sheet (JPG, PNG, WebP up to 1800 px) in under 0.05 seconds with 0 bytes uploaded externally.
InkStudio Step 2 (Toggle Pro Morphological Switches & SDF Stroke Morphing): Enable Overlapping Black Text Inpainting (1–12 px radius), Notebook Ruled/Grid Line Stripping, and 2D Euclidean SDF Stroke Morphing (-2.5 px to +4.5 px) while choosing from 6 de-haloed ink color presets.
InkStudio Step 3 (Preview on Interactive Contract Simulator & Export PNG / SVG): Inspect transparency across 5 views (including the live draggable Electronic Contract Stamp Simulator and dark-mode halo check) and export lossless 32-bit RGBA PNG or Ramer-Douglas-Peucker simplified vector SVG.
Frequently Asked Questions (FAQ)
- Why does InkStudio extract cleaner signatures and red seals than generic AI background removers?
- InkStudio models the physical paper-and-ink transmittance using Beer-Lambert continuous optical density unmixing and solves true foreground color F = (I - (1 - alpha)B) / alpha. This preserves inner letter loops and dry-brush flying-white bristles while eliminating the 1–3 px white paper halos left by generic salient-object segmentation.
- How does InkStudio remove black contract text overlapping a red seal and heal the gaps?
- InkStudio identifies dark achromatic contract text pixels (absorption > 28% and redness delta < 14%) crossing crimson seal regions, strips them to 0 alpha, and runs iterative 8-neighbor directional morphological inpainting (1–12 px radius) so surrounding vermilion seal strokes bridge across the gap seamlessly.
- How does InkStudio strip notebook ruled lines and calligraphy grids without breaking handwriting strokes?
- InkStudio combines chromaticity excess filtering (blue, green, and faint gray lines) with horizontal and vertical run-length projection while checking perpendicular gradient continuity +-4 px across each line, preserving dark handwriting crossings 100% intact.
- How does InkStudio 2D Euclidean SDF stroke thickening differ from standard dilation?
- InkStudio computes the exact O(N) Felzenszwalb-Huttenlocher 2D Euclidean Distance Transform (EDT) via lower envelopes of parabolas and shifts the continuous signed distance zero-level set from -2.5 px to +4.5 px with 0.85 px smoothstep anti-aliasing, turning faint ballpoint strokes into bold fountain-pen ink with zero boxy artifacts.
- Does InkStudio upload my signatures, company seals, or contracts to any server?
- InkStudio uploads 0 bytes of your images, signatures, seals, or contracts; 100% of optical unmixing, SDF morphing, and SVG contour tracing executes locally in browser WebAssembly linear memory over HTTPS, storing only your 4 languages UI preference in localStorage.