【Engineer-Made】The Inside Story and User Guide for ‘Benri-Kit’: A Free, Secure Suite of PDF/Image Editing Tools
1. Introduction: The Motivation Behind Development and My Thoughts as an Engineer
In system development and administrative work, minor needs frequently arise, such as “I just want to delete one page from a PDF” or “I want to consolidate documents into one file.” However, professional-grade editing software is expensive, making its adoption a significant hurdle in reality.
Furthermore, even after purchasing editing software, a psychological bottleneck often arises: “I want to do this myself, but I don't know how.” This frequently led to the uncomfortable routine of busy designers halting their work to request corrections. As an engineer, I wondered: Couldn't this “inconvenience” be solved? It was this pure motivation that gave birth to the browser-based toolset ‘Benri-Kit’.
The driving force was the desire to create tools that make “tomorrow's work” lighter and safer!
2. Key Feature: “Overwhelmingly Secure Design” – Files Never Leave Your Device
The core concept of this tool is “Security by Design.” Unlike typical online editing services, user files are never transmitted over the network to external servers.
How it works: Local processing logic within the browser
All file merging and image processing is executed by libraries (such as pdf-lib, Canvas API, OffscreenCanvas) running within the user's own PC browser. This means the user's CPU performs the calculations directly, eliminating upload latency and guaranteeing ultimate privacy.
Four Properties Supporting Non-Destructive & Non-Recording
* No Network Communication: No communication with external servers occurs during processing.
* Non-destructive editing: Processing occurs in browser memory; original files on the PC are never directly overwritten.
* Complete memory erasure: Loaded data is stored only in the browser's temporary memory and is completely erased without a trace when the tab is closed.
* Server non-recording: Inputs for IP diagnostics and asset simulators are designed to be “disposable”—nothing is saved on the server.
3. PDF Toolkit: No More Editing Software Confusion
Handle essential PDF editing for business documents without specialized software.
* Merge & Rearrange: Combine multiple files via drag-and-drop. Links and form fields within pages are generally preserved (※Bookmarks may not carry over due to library constraints).
* Rotate & Delete Pages: Uses a “metadata-only” rewrite method, avoiding image re-encoding and ensuring zero quality loss. Ideal for correcting orientation errors from scans.
* Text Extraction: Utilizes PDF.js to estimate headings based on font size (sizes 1.3x or larger are identified as ###). Outputs in Markdown format for seamless migration to Notion or GitHub.
* Watermark: Applies uniformly to all pages.
* Engineer-Recommended Settings: Set angle to “-45°” and opacity to “15–25%” to achieve a “diagonal watermark” that provides strong deterrence without compromising readability.
4. Image Toolkit: WebP Conversion and Privacy Protection
Features image optimization and functions to eliminate risks specific to digital data.
WebP Conversion with Exceptional Compression Rates
Convert JPEG or PNG files to the next-generation format “WebP”. WebP reduces file size by 25-35% compared to equivalent-quality JPEGs, making it highly effective for lightening websites and saving storage space.
Automatic EXIF Data Removal to Prevent Unintended Information Leaks
Through a redrawing process using the Canvas API, GPS location data and capture timestamps (EXIF information) embedded in photos are automatically removed. This engineering solution makes privacy protection “standard practice” when posting to social media.
Japanese-Language Watermark Support
Image watermarks fully support Japanese text (“Confidential,” “Sample,” etc.). The “Tile Mode” particularly covers the entire image, making it difficult to remove the watermark through cropping.
5. Business and Developer Tools to Accelerate Work Efficiency
A suite of tools addressing pain points in both administrative tasks and development work.
* Digital Seal Maker: Creates personal seals (10.5mm), square seals (21mm), and date stamps. Designed at professional 350 DPI resolution, it reproduces sharp, true-to-size impressions when pasted into Word or Excel for printing. “Smudged” effects eliminate digital coldness, imparting a realistic texture.
* Sequential Renamer: Batch process files regardless of format. Reflects OS filename sorting or manual rearrangement, enabling bulk ZIP downloads.
* Developer Tools: Covers daily conversion needs like JSON formatting (Pretty Print/Minify), BASE64, URL encoding, and Unicode conversion.
* IP Diagnosis & Fund Simulator: IP diagnosis using “heuristic detection (inference from connection info)” without relying on external APIs, and a simulator calculating theoretical compound interest values—all powered solely by browser-based logic.
6. Frequently Asked Questions (FAQ): To Start Using with Confidence
Q. Is data truly never sent to a server?
A. Yes. All processing occurs entirely within your local browser, allowing you to safely handle highly confidential company documents and personal photos.
Q. Are there limits on the number or size of files I can process?
A. Processing capacity depends on your browser's memory. As a guideline, it operates stably for “up to 100MB total or 50 files.” Exceeding this may cause browser instability, so we recommend splitting files for processing.
Q. Can password-protected PDFs be processed?
A. Password-protected files will cause errors during loading. Please remove the password beforehand.
7. Closing Thoughts: A Safe and Convenient Tool for Everyone
At the core of ‘Benri-Kit’ lies an engineer's desire: “To use technology sincerely and eliminate user inconvenience.” There's no need to wait for expensive software or fear information leaks to external parties.
We hope this tool makes your “tomorrow's tasks” a little smarter and helps free up time for the creative work you should be focusing on. Please bookmark it and use it as your go-to “toolbox” when you need help.