pdfium_bindings 1.0.0

This project aims to wrap the complete [Pdfium](https://pdfium.googlesource.com/pdfium/) API in dart, over FFI.

pdfium_bindings

This project aims to wrap the complete Pdfium API in dart, over FFI.

Example:

import 'dart:ffi';
import 'dart:io';

import 'package:ffi/ffi.dart';
import 'package:pdfium_bindings/pdfium_bindings.dart';
import 'package:path/path.dart' as path;
import 'package:pdfium_bindings/src/utils.dart';
import 'package:image/image.dart';

void main() {
  //the dynamic library path  
  var libraryPath = path.join(Directory.current.path, 'pdfium.dll');
  final dylib = DynamicLibrary.open(libraryPath);
  var pdfium = PDFiumBindings(dylib);
  //memory allocator
  var allocate = calloc;
  //initialize library 
  final config = allocate<FPDF_LIBRARY_CONFIG>();
  config.ref.version = 2;
  config.ref.m_pUserFontPaths = nullptr;
  config.ref.m_pIsolate = nullptr;
  config.ref.m_v8EmbedderSlot = 0;
  pdfium.FPDF_InitLibraryWithConfig(config);

  //input PDF file 
  var filePathP = stringToNativeInt8('1417.pdf');
  //load document
  var doc = pdfium.FPDF_LoadDocument(filePathP, nullptr);
  if (doc == nullptr) {
    var err = pdfium.FPDF_GetLastError();
    throw PdfiumException.fromErrorCode(err);
  }
  var pageCount = pdfium.FPDF_GetPageCount(doc);
  print('pageCount: $pageCount');
  //load first page
  var page = pdfium.FPDF_LoadPage(doc, 0);
  if (page == nullptr) {
    var err = pdfium.getLastErrorMessage();
    pdfium.FPDF_CloseDocument(doc);
    throw PageException(message: err);
  }
  var scale = 1;
  var width = (pdfium.FPDF_GetPageWidth(page) * scale).round();
  var height = (pdfium.FPDF_GetPageHeight(page) * scale).round();

  print('page Width: $width');
  print('page Height: $height');

  // var backgroundStr = "FFFFFFFF"; // as int 268435455
  var background = 268435455;
  var start_x = 0;
  var size_x = width;
  var start_y = 0;
  var size_y = height;
  var rotate = 0;

  // Create empty bitmap and render page onto it
  // The bitmap always uses 4 bytes per pixel. The first byte is always
  // double word aligned.
  // The byte order is BGRx (the last byte unused if no alpha channel) or
  // BGRA.
  var bitmap = pdfium.FPDFBitmap_Create(width, height, 0);
  pdfium.FPDFBitmap_FillRect(bitmap, 0, 0, width, height, background);
  pdfium.FPDF_RenderPageBitmap(bitmap, page, start_x, start_y, size_x, size_y,
      rotate, FPDF_ANNOT | FPDF_LCD_TEXT);

  //  The pointer to the first byte of the bitmap buffer The data is in BGRA format
  var pointer = pdfium.FPDFBitmap_GetBuffer(bitmap).cast<Uint8>();
  //stride = width * 4 bytes per pixel BGRA
  var stride = pdfium.FPDFBitmap_GetStride(bitmap);
  print('stride $stride');

  var image = Image.fromBytes(
      width, height, pointer.asTypedList(width * height * 4),
      format: Format.bgra, channels: Channels.rgba);

  // save bitmap as PNG.
  File('out.png').writeAsBytesSync(encodePng(image));

  //clean memory
  allocate.free(bitmap);
  allocate.free(pointer);

  pdfium.FPDF_ClosePage(page);
  allocate.free(filePathP);

  pdfium.FPDF_DestroyLibrary();
  allocate.free(config);
}

This has the potential to build a truly cross platform, high-level API for rendering and editing PDFs on all 5 platforms.

Goals

• Build Pdfium shared libraries for all platforms. (pdfium-binaries)
• Find a way to generate FFI code from C headers. (ffigen)
• Integrate into flutter_pdf_viewer.

Thanks

A scientifichackers for inspiring me A big THANK YOU to Google for open sourcing Pdfium, and releasing dart:ffi.