Merge pull request #9729 from Snuffleupagus/gulp-image_decoders

Add a `gulp image_decoders` command to package the image decoders (i.e. jpg.js, jpx.js, jbig2.js) separately, and publish them in pdfjs-dist

src/core/jbig2.js

@@ -1192,6 +1192,47 @@ var Jbig2Image = (function Jbig2ImageClosure() {
     return visitor.buffer;
   }
 
+  function parseJbig2(data) {
+    let position = 0, end = data.length;
+
+    if (data[position] !== 0x97 || data[position + 1] !== 0x4A ||
+        data[position + 2] !== 0x42 || data[position + 3] !== 0x32 ||
+        data[position + 4] !== 0x0D || data[position + 5] !== 0x0A ||
+        data[position + 6] !== 0x1A || data[position + 7] !== 0x0A) {
+      throw new Jbig2Error('parseJbig2 - invalid header.');
+    }
+
+    let header = Object.create(null);
+    position += 8;
+    const flags = data[position++];
+    header.randomAccess = !(flags & 1);
+    if (!(flags & 2)) {
+      header.numberOfPages = readUint32(data, position);
+      position += 4;
+    }
+
+    let segments = readSegments(header, data, position, end);
+    let visitor = new SimpleSegmentVisitor();
+    processSegments(segments, visitor);
+
+    const { width, height, } = visitor.currentPageInfo;
+    const bitPacked = visitor.buffer;
+    let imgData = new Uint8ClampedArray(width * height);
+    let q = 0, k = 0;
+    for (let i = 0; i < height; i++) {
+      let mask = 0, buffer;
+      for (let j = 0; j < width; j++) {
+        if (!mask) {
+          mask = 128; buffer = bitPacked[k++];
+        }
+        imgData[q++] = (buffer & mask) ? 0 : 255;
+        mask >>= 1;
+      }
+    }
+
+    return { imgData, width, height, };
+  }
+
   function SimpleSegmentVisitor() {}
 
   SimpleSegmentVisitor.prototype = {
@@ -2095,9 +2136,16 @@ var Jbig2Image = (function Jbig2ImageClosure() {
   function Jbig2Image() {}
 
   Jbig2Image.prototype = {
-    parseChunks: function Jbig2Image_parseChunks(chunks) {
+    parseChunks(chunks) {
       return parseJbig2Chunks(chunks);
     },
+
+    parse(data) {
+      const { imgData, width, height, } = parseJbig2(data);
+      this.width = width;
+      this.height = height;
+      return imgData;
+    },
   };
 
   return Jbig2Image;

src/core/jpeg_stream.js

@@ -63,7 +63,10 @@ let JpegStream = (function JpegStreamClosure() {
     if (this.eof) {
       return;
     }
-    let jpegImage = new JpegImage();
+    let jpegOptions = {
+      decodeTransform: undefined,
+      colorTransform: undefined,
+    };
 
     // Checking if values need to be transformed before conversion.
     let decodeArr = this.dict.getArray('Decode', 'D');
@@ -81,16 +84,17 @@ let JpegStream = (function JpegStreamClosure() {
         }
       }
       if (transformNeeded) {
-        jpegImage.decodeTransform = transform;
+        jpegOptions.decodeTransform = transform;
       }
     }
     // Fetching the 'ColorTransform' entry, if it exists.
     if (isDict(this.params)) {
       let colorTransform = this.params.get('ColorTransform');
       if (Number.isInteger(colorTransform)) {
-        jpegImage.colorTransform = colorTransform;
+        jpegOptions.colorTransform = colorTransform;
       }
     }
+    const jpegImage = new JpegImage(jpegOptions);
 
     jpegImage.parse(this.bytes);
     let data = jpegImage.getData(this.drawWidth, this.drawHeight,

src/core/jpg.js

@@ -94,9 +94,9 @@ var JpegImage = (function JpegImageClosure() {
   var dctSqrt2 =  5793;   // sqrt(2)
   var dctSqrt1d2 = 2896;  // sqrt(2) / 2
 
-  function JpegImage() {
-    this.decodeTransform = null;
-    this.colorTransform = -1;
+  function JpegImage({ decodeTransform = null, colorTransform = -1, } = {}) {
+    this._decodeTransform = decodeTransform;
+    this._colorTransform = colorTransform;
   }
 
   function buildHuffmanTable(codeLengths, values) {
@@ -1013,7 +1013,7 @@ var JpegImage = (function JpegImageClosure() {
       }
 
       // decodeTransform contains pairs of multiplier (-256..256) and additive
-      var transform = this.decodeTransform;
+      const transform = this._decodeTransform;
       if (transform) {
         for (i = 0; i < dataLength;) {
           for (j = 0, k = 0; j < numComponents; j++, i++, k += 2) {
@@ -1030,7 +1030,7 @@ var JpegImage = (function JpegImageClosure() {
         return !!this.adobe.transformCode;
       }
       if (this.numComponents === 3) {
-        if (this.colorTransform === 0) {
+        if (this._colorTransform === 0) {
           // If the Adobe transform marker is not present and the image
           // dictionary has a 'ColorTransform' entry, explicitly set to `0`,
           // then the colours should *not* be transformed.
@@ -1039,7 +1039,7 @@ var JpegImage = (function JpegImageClosure() {
         return true;
       }
       // `this.numComponents !== 3`
-      if (this.colorTransform === 1) {
+      if (this._colorTransform === 1) {
         // If the Adobe transform marker is not present and the image
         // dictionary has a 'ColorTransform' entry, explicitly set to `1`,
         // then the colours should be transformed.

src/pdf.image_decoders.js

@@ -0,0 +1,45 @@
+/* Copyright 2018 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.
+ */
+/* eslint-disable no-unused-vars */
+
+import { getVerbosityLevel, setVerbosityLevel } from './shared/util';
+import { Jbig2mage } from './core/jbig2';
+import { JpegImage } from './core/jpg';
+import { JpxImage } from './core/jpx';
+
+// To ensure that the standalone PDF.js image decoders have the same
+// browser/environment compatibility as the regular PDF.js library,
+// the standard set of polyfills are thus included in this build as well.
+//
+// Given that the (current) image decoders don't use all of the features
+// of the complete PDF.js library, e.g. they are completely synchronous,
+// some of the larger polyfills are thus unnecessary.
+//
+// In an attempt to reduce the size of the standalone PDF.js image decoders,
+// the following polyfills are currently being excluded:
+//  - ReadableStream
+//  - Promise
+//  - URL
+
+const pdfjsVersion = PDFJSDev.eval('BUNDLE_VERSION');
+const pdfjsBuild = PDFJSDev.eval('BUNDLE_BUILD');
+
+export {
+  Jbig2mage,
+  JpegImage,
+  JpxImage,
+  getVerbosityLevel,
+  setVerbosityLevel,
+};

src/shared/compatibility.js

@@ -147,6 +147,11 @@ const hasDOM = typeof window === 'object' && typeof document === 'object';
 
 // Support: IE, Safari<8, Chrome<32
 (function checkPromise() {
+  if (typeof PDFJSDev !== 'undefined' && PDFJSDev.test('IMAGE_DECODERS')) {
+    // The current image decoders are synchronous, hence `Promise` shouldn't
+    // need to be polyfilled for the IMAGE_DECODERS build target.
+    return;
+  }
   if (globalScope.Promise) {
     return;
   }
@@ -166,6 +171,11 @@ const hasDOM = typeof window === 'object' && typeof document === 'object';
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 (function checkURLConstructor() {
+  if (typeof PDFJSDev !== 'undefined' && PDFJSDev.test('IMAGE_DECODERS')) {
+    // The current image decoders doesn't utilize the `URL` constructor, hence
+    // it shouldn't need to be polyfilled for the IMAGE_DECODERS build target.
+    return;
+  }
   // feature detect for URL constructor
   var hasWorkingUrl = false;
   try {

src/shared/streams_polyfill.js

@@ -31,6 +31,17 @@ if (typeof ReadableStream !== 'undefined') {
 if (isReadableStreamSupported) {
   exports.ReadableStream = ReadableStream;
 } else {
-  exports.ReadableStream =
-    require('../../external/streams/streams-lib').ReadableStream;
+  if (typeof PDFJSDev !== 'undefined' && PDFJSDev.test('IMAGE_DECODERS')) {
+    class DummyReadableStream {
+      constructor() {
+        throw new Error('The current image decoders are synchronous, ' +
+                        'hence `ReadableStream` shouldn\'t need to be ' +
+                        'polyfilled for the IMAGE_DECODERS build target.');
+      }
+    }
+    exports.ReadableStream = DummyReadableStream;
+  } else {
+    exports.ReadableStream =
+      require('../../external/streams/streams-lib').ReadableStream;
+  }
 }