Use the PDFium JBig2 decoder compiled into wasm

The decoder is ~4x faster than the JS decoder on large images.

eslint.config.mjs

@@ -35,6 +35,7 @@ export default [
       "external/builder/fixtures_babel/",
       "external/openjpeg/",
       "external/qcms/",
+      "external/jbig2/",
       "external/quickjs/",
       "test/stats/results/",
       "test/tmp/",

external/jbig2/LICENSE_JBIG2

@@ -0,0 +1,196 @@
+// Copyright 2014 The PDFium Authors
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+                                 Apache License
+                           Version 2.0, January 2004
+                        https://www.apache.org/licenses/
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+   1. Definitions.
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+   END OF TERMS AND CONDITIONS
+   APPENDIX: How to apply the Apache License to your work.
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "[]"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+   Copyright [yyyy] [name of copyright owner]
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+       https://www.apache.org/licenses/LICENSE-2.0
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.

external/jbig2/LICENSE_PDFJS_JBIG2

@@ -0,0 +1,13 @@
+Copyright 2026 Mozilla Foundation
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.

external/jbig2/README.md

@@ -0,0 +1,12 @@
+## Build
+
+In order to generate the file `jbig2.js`:
+* git clone https://github.com/mozilla/pdf.js.jbig2/
+* the build requires to have a [Docker](https://www.docker.com/) setup and then:
+  * `node build.js -C` to build the Docker image
+  * `node build.js -co /pdf.js/external/jbig2/` to compile the decoder
+
+## Licensing
+
+[PDFium](https://pdfium.googlesource.com/pdfium/) is under [Apache-2.0](https://pdfium.googlesource.com/pdfium/+/main/LICENSE)
+and [pdf.js.jbig2](https://github.com/mozilla/pdf.js.jbig2/) is released under [Apache-2.0](https://github.com/mozilla/pdf.js.jbig2/blob/main/LICENSE) license so `jbig2.js` is released under [Apache-2.0](https://github.com/mozilla/pdf.js.jbig2/blob/main/LICENSE) license too.

gulpfile.mjs

@@ -696,6 +696,10 @@ function createWasmBundle() {
       base: "external/qcms",
       encoding: false,
     }),
+    gulp.src(["external/jbig2/*.wasm", "external/jbig2/LICENSE_*"], {
+      base: "external/jbig2",
+      encoding: false,
+    }),
   ]);
 }
 
@@ -1696,6 +1700,7 @@ function buildLib(defines, dir) {
     gulp.src("test/unit/*.js", { base: ".", encoding: false }),
     gulp.src("external/openjpeg/*.js", { base: "openjpeg/", encoding: false }),
     gulp.src("external/qcms/*.js", { base: "qcms/", encoding: false }),
+    gulp.src("external/jbig2/*.js", { base: "jbig2/", encoding: false }),
   ]);
 
   return buildLibHelper(bundleDefines, inputStream, dir);
@@ -2207,7 +2212,7 @@ gulp.task(
     },
     function watchWasm() {
       gulp.watch(
-        ["external/openjpeg/*", "external/qcms/*"],
+        ["external/openjpeg/*", "external/qcms/*", "external/jbig2/*"],
         { ignoreInitial: false },
         gulp.series("dev-wasm")
       );

src/core/image.js

@@ -369,7 +369,7 @@ class PDFImage {
     const inverseDecode = decode?.[0] > 0;
 
     const computedLength = ((width + 7) >> 3) * height;
-    const imgArray = image.getBytes(computedLength);
+    const imgArray = await image.getImageData(computedLength);
 
     const isSingleOpaquePixel =
       width === 1 &&

src/core/jbig2_stream.js

@@ -13,11 +13,12 @@
  * limitations under the License.
  */
 
+import { shadow, warn } from "../shared/util.js";
 import { BaseStream } from "./base_stream.js";
 import { DecodeStream } from "./decode_stream.js";
 import { Dict } from "./primitives.js";
 import { Jbig2Image } from "./jbig2.js";
-import { shadow } from "../shared/util.js";
+import { JBig2WasmImage } from "./jbig2_wasm.js";
 
 /**
  * For JBIG2's we use a library to decode these images and
@@ -47,7 +48,40 @@ class Jbig2Stream extends DecodeStream {
     this.decodeImage();
   }
 
-  decodeImage(bytes) {
+  get isAsyncDecoder() {
+    return true;
+  }
+
+  async decodeImage(bytes, _decoderOptions) {
+    if (this.eof) {
+      return this.buffer;
+    }
+    bytes ||= this.bytes;
+    try {
+      let globals = null;
+      if (this.params instanceof Dict) {
+        const globalsStream = this.params.get("JBIG2Globals");
+        if (globalsStream instanceof BaseStream) {
+          globals = globalsStream.getBytes();
+        }
+      }
+      this.buffer = await JBig2WasmImage.decode(
+        bytes,
+        this.dict.get("Width"),
+        this.dict.get("Height"),
+        globals
+      );
+    } catch {
+      warn("Jbig2Stream: Falling back to JS JBIG2 decoder.");
+      return this.decodeImageFallback(bytes);
+    }
+    this.bufferLength = this.buffer.length;
+    this.eof = true;
+
+    return this.buffer;
+  }
+
+  async decodeImageFallback(bytes) {
     if (this.eof) {
       return this.buffer;
     }

src/core/jbig2_wasm.js

@@ -0,0 +1,127 @@
+/* Copyright 2026 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { BaseException, warn } from "../shared/util.js";
+import { fetchBinaryData } from "./core_utils.js";
+import JBig2 from "../../external/jbig2/jbig2.js";
+
+class JBig2Error extends BaseException {
+  constructor(msg) {
+    super(msg, "Jbig2Error");
+  }
+}
+
+class JBig2WasmImage {
+  static #buffer = null;
+
+  static #handler = null;
+
+  static #modulePromise = null;
+
+  static #useWasm = true;
+
+  static #useWorkerFetch = true;
+
+  static #wasmUrl = null;
+
+  static setOptions({ handler, useWasm, useWorkerFetch, wasmUrl }) {
+    this.#useWasm = useWasm;
+    this.#useWorkerFetch = useWorkerFetch;
+    this.#wasmUrl = wasmUrl;
+
+    if (!useWorkerFetch) {
+      this.#handler = handler;
+    }
+  }
+
+  static async #instantiateWasm(fallbackCallback, imports, successCallback) {
+    const filename = "jbig2.wasm";
+    try {
+      if (!this.#buffer) {
+        if (this.#useWorkerFetch) {
+          this.#buffer = await fetchBinaryData(`${this.#wasmUrl}${filename}`);
+        } else {
+          this.#buffer = await this.#handler.sendWithPromise(
+            "FetchBinaryData",
+            { type: "wasmFactory", filename }
+          );
+        }
+      }
+      const results = await WebAssembly.instantiate(this.#buffer, imports);
+      return successCallback(results.instance);
+    } catch (reason) {
+      warn(`JBig2Image#instantiateWasm: ${reason}`);
+      return null;
+    } finally {
+      this.#handler = null;
+    }
+  }
+
+  static async decode(bytes, width, height, globals) {
+    if (!this.#modulePromise) {
+      const { promise, resolve } = Promise.withResolvers();
+      const promises = [promise];
+      if (this.#useWasm) {
+        promises.push(
+          JBig2({
+            warn,
+            instantiateWasm: this.#instantiateWasm.bind(this, resolve),
+          })
+        );
+      } else {
+        resolve(null);
+      }
+      this.#modulePromise = Promise.race(promises);
+    }
+    const module = await this.#modulePromise;
+    if (!module) {
+      throw new JBig2Error("JBig2 failed to initialize");
+    }
+    let ptr, globalsPtr;
+
+    try {
+      const size = bytes.length;
+      ptr = module._malloc(size);
+      module.writeArrayToMemory(bytes, ptr);
+      const globalsSize = globals ? globals.length : 0;
+      if (globalsSize > 0) {
+        globalsPtr = module._malloc(globalsSize);
+        module.writeArrayToMemory(globals, globalsPtr);
+      }
+
+      module._jbig2_decode(ptr, size, width, height, globalsPtr, globalsSize);
+      if (!module.imageData) {
+        throw new JBig2Error("Unknown error");
+      }
+      const { imageData } = module;
+      module.imageData = null;
+
+      return imageData;
+    } finally {
+      if (ptr) {
+        module._free(ptr);
+      }
+      if (globalsPtr) {
+        module._free(globalsPtr);
+      }
+    }
+  }
+
+  static cleanup() {
+    this.#modulePromise = null;
+  }
+}
+
+export { JBig2Error, JBig2WasmImage };

src/core/pdf_manager.js

@@ -22,6 +22,7 @@ import {
 } from "../shared/util.js";
 import { ChunkedStreamManager } from "./chunked_stream.js";
 import { ImageResizer } from "./image_resizer.js";
+import { JBig2WasmImage } from "./jbig2_wasm.js";
 import { JpegStream } from "./jpeg_stream.js";
 import { JpxImage } from "./jpx.js";
 import { MissingDataException } from "./core_utils.js";
@@ -81,6 +82,7 @@ class BasePdfManager {
     JpxImage.setOptions(options);
     IccColorSpace.setOptions(options);
     CmykICCBasedCS.setOptions(options);
+    JBig2WasmImage.setOptions(options);
   }
 
   get docId() {

test/pdfs/JBIG2Globals.pdf.link

@@ -0,0 +1 @@
+https://github.com/pdfminer/pdfminer.six/files/8399364/64.pdf

test/test_manifest.json

@@ -13131,5 +13131,13 @@
     "rounds": 1,
     "link": true,
     "type": "eq"
+  },
+  {
+    "id": "JBIG2Globals",
+    "file": "pdfs/JBIG2Globals.pdf",
+    "md5": "78ee015a604678a4efbdcd993e0d77aa",
+    "rounds": 1,
+    "link": true,
+    "type": "eq"
   }
 ]