9654ad570a
Getting images is already asynchronous, so we can use this opportunity to use DecompressStream (which is async too) to decompress images.
86 lines
2.4 KiB
JavaScript
86 lines
2.4 KiB
JavaScript
/* Copyright 2012 Mozilla Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import { BaseStream } from "./base_stream.js";
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import { DecodeStream } from "./decode_stream.js";
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import { Dict } from "./primitives.js";
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import { Jbig2Image } from "./jbig2.js";
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import { shadow } from "../shared/util.js";
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/**
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* For JBIG2's we use a library to decode these images and
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* the stream behaves like all the other DecodeStreams.
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*/
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class Jbig2Stream extends DecodeStream {
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constructor(stream, maybeLength, params) {
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super(maybeLength);
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this.stream = stream;
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this.dict = stream.dict;
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this.maybeLength = maybeLength;
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this.params = params;
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}
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get bytes() {
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// If `this.maybeLength` is null, we'll get the entire stream.
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return shadow(this, "bytes", this.stream.getBytes(this.maybeLength));
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}
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ensureBuffer(requested) {
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// No-op, since `this.readBlock` will always parse the entire image and
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// directly insert all of its data into `this.buffer`.
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}
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readBlock() {
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this.decodeImage();
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}
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decodeImage(bytes) {
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if (this.eof) {
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return this.buffer;
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}
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bytes ||= this.bytes;
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const jbig2Image = new Jbig2Image();
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const chunks = [];
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if (this.params instanceof Dict) {
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const globalsStream = this.params.get("JBIG2Globals");
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if (globalsStream instanceof BaseStream) {
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const globals = globalsStream.getBytes();
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chunks.push({ data: globals, start: 0, end: globals.length });
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}
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}
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chunks.push({ data: bytes, start: 0, end: bytes.length });
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const data = jbig2Image.parseChunks(chunks);
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const dataLength = data.length;
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// JBIG2 had black as 1 and white as 0, inverting the colors
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for (let i = 0; i < dataLength; i++) {
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data[i] ^= 0xff;
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}
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this.buffer = data;
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this.bufferLength = dataLength;
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this.eof = true;
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return this.buffer;
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}
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get canAsyncDecodeImageFromBuffer() {
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return this.stream.isAsync;
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}
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}
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export { Jbig2Stream };
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