PDFCoriumKit

Cross‑platform PDF tooling built on the open‑source PDFium engine (Chromium) via its public C API.

• Android: JNI bridge + demo app
• iOS: Swift wrapper + SwiftUI demo
• Web: WASM adapter + browser demo

Highlights

• Open PDFs (with optional passwords)
• Render pages to bitmaps/canvas
• Interactive form support (focus, select/replace text, list/checkbox helpers)
• Basic annotation helpers (ink, highlight, rectangle, text insertion)
• Save updated documents (file or Blob)
• Progressive loading on Web via FPDFAvail when available
• Small, readable bridges intended for embedding and extension

Repository Layout

• android/ — Android library (pdfiumkit) and demo app
• ios/ — Swift wrapper library (PdfiumKit) and SwiftUI demo app
• web/ — Standalone browser demo using PDFium WASM

Paths below are relative to this sdk/ folder.

Android

• minSdk 21, target/compileSdk 34
• Requires NDK + CMake (AGP wires CMake 3.22.1)
• PDFium artifacts expected at:
  • Headers: src-android/pdfium/public
  • Libraries: out/android/release/lib/<abi>/libpdfium.a

Open android/ in Android Studio and build the demo module. Gradle passes the following to CMake:

• PDFIUM_HEADERS_DIR → src-android/pdfium/public
• PDFIUM_LIB_DIR → out/android/release/lib

Quick start (Java):

PdfiumDocument doc = new PdfiumDocument();
doc.open("/sdcard/Download/sample.pdf"); // optional password overload available
long page = doc.loadPage(0);
float w = doc.getPageWidth(page), h = doc.getPageHeight(page);

Bitmap bmp = Bitmap.createBitmap(Math.max(1, (int) w), Math.max(1, (int) h), Bitmap.Config.ARGB_8888);
// FPDF_ANNOT flag included so annotations render too (flag == 1)
doc.renderPageBitmap(page, bmp, 0, 0, bmp.getWidth(), bmp.getHeight(), 0, 1);

// Simple form fill example at page coordinates:
if (doc.focusFormAt(page, 100f, 120f)) {
  doc.formSelectAll(page);
  doc.formReplaceSelection(page, "John Doe");
}

boolean saved = doc.save(getCacheDir() + "/edited.pdf");

doc.closePage(page);
doc.close();

Notes

• Ensure libpdfium.a is built and placed for each ABI under out/android/release/lib/<abi>/.
• The JNI bridge initializes PDFium once and manages a minimal form‑fill environment.

iOS

• Library Xcode project: ios/PdfiumKit/PdfiumKit.xcodeproj
• SwiftUI demo: ios/PdfiumKitDemo/PdfiumKitDemo.xcodeproj
• The project references a pdfium.xcframework. By default, the reference points to out/ios/release/pdfium.xcframework (relative to the repository). If you rebuild or relocate it, update the Xcode reference accordingly.

Quick start (Swift):

import PdfiumKit

let doc = try FPDocument(url: inputURL)
let page = try doc.page(index: 0)
let form = FPForm(document: doc)

let image = PdfRenderer.render(page: page, form: form, targetWidth: 1200)
// Fill a text widget if tapped location maps to a field
if let annot = form.formField(at: CGPoint(x: 100, y: 120), on: page) {
    _ = form.setFocused(annot)
    form.replaceSelection(on: page, text: "John Doe")
}

try doc.save(to: outputURL)

Notes

• FPDocument is a thin RAII wrapper around a PDFium document.
• FPForm manages the form‑fill environment and helpers (focus, selection, values).
• PdfRenderer draws the page and overlays widgets.

Web

• Plain HTML/JS demo using Emscripten glue if present; falls back to direct WASM instantiation.
• Files:
  • web/index.html, web/styles.css
  • web/lib/pdfium.js, web/lib/pdfium.wasm
  • web/pdfiumkit.js (adapter), web/app.js (demo wiring)

Serve the folder over HTTP (WASM requires it). Examples:

• Python: cd web && python3 -m http.server
• Node: npx serve web

Quick start (JavaScript):

const adapter = new PdfiumAdapter();
await adapter.init();

const buf = await (await fetch('sample.pdf')).arrayBuffer();
const doc = await adapter.loadDocumentFromArrayBuffer(buf);
const page = adapter.loadPage(doc, 0);

adapter.renderPageToCanvas(page, document.querySelector('#pageCanvas'), {
  targetWidth: 1200,
  devicePixelRatio: window.devicePixelRatio || 1
});

// Form example: set value for first detected text field (if any)
const widgets = adapter.listWidgetFields(page);
if (widgets && widgets.length) {
  adapter.setTextFieldValue(widgets[0], 'John Doe');
}

// Save to Blob
const blob = adapter.saveDocument(doc);
// ... trigger download or upload ...

adapter.closePage(page);
adapter.closeDocument(doc);

Notes

• The adapter exposes rendering, annotations (ink/highlight/rect), basic text insertion, widget helpers, and saving.
• Progressive loading via FPDFAvail_* is used when available.

Building PDFium (Overview)

PdfiumKit assumes you provide PDFium binaries and public headers.

• Android
  • Build PDFium static libraries for armeabi-v7a, arm64-v8a, x86, x86_64.
  • Place headers under src-android/pdfium/public and libs under out/android/release/lib/<abi>/libpdfium.a.
• iOS
  • Provide out/ios/release/pdfium.xcframework (the Xcode project references this path).
  • If you rebuild PDFium, replace the xcframework and ensure its public headers are included within it.
• Web
  • web/lib/pdfium.js and web/lib/pdfium.wasm are included for the demo. If you rebuild, drop‑in replace them.

Refer to the upstream PDFium build documentation for platform‑specific steps (including flags for form filling, saving, etc.).

Status & Limitations

• Bridges focus on core flows; many advanced PDFium APIs are not wrapped.

• Some Web features are not implemented or are stubbed (e.g., full flattening pipeline, rich FreeText editing).

• Android build expects external PDFium artifacts; verify paths in android/pdfiumkit/build.gradle if customizing.

• Built on PDFium (Chromium).

Releases

Android

• Prereqs: JDK 17, Android SDK, NDK 26.1.10909125, CMake 3.22.1.
• Provide PDFium for Android:
  • Headers at src-android/pdfium/public (path contains public/fpdfview.h).
  • Static libs at out/android/release/lib/<abi>/libpdfium.a for armeabi-v7a, arm64-v8a, x86, x86_64.
• Build AAR:
  • cd android
  • ./gradlew :pdfiumkit:assembleRelease
  • Artifact: android/pdfiumkit/build/outputs/aar/pdfiumkit-release.aar
• Note: The module is wired to link against libpdfium.a.

iOS

• Prereqs: Xcode (CLT) on macOS.
• Build XCFramework:
  • cd ios/PdfiumKit
  • ./build_xcframework.sh
  • Artifact: ios/PdfiumKit/build/PdfiumKit.xcframework
• The script auto-detects headers from ios/PdfiumKit/lib/pdfium.xcframework, so no extra setup is needed.

Web

• Prereqs: none (assets already built).
• Publish/Serve:
  • The web/ folder is ready to host as-is.
  • Serve locally for testing: cd web && python3 -m http.server or npx serve web.
  • For deployment, copy the contents of web/ to your static host or CDN. Ensure lib/pdfium.wasm is served with MIME application/wasm and appropriate CORS if loaded cross-origin.