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105 lines
2.9 KiB
JavaScript
105 lines
2.9 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 { JBig2CCITTFaxImage } from "./jbig2_ccittFax.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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get isAsyncDecoder() {
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return true;
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}
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get isImageStream() {
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return true;
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}
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// The JBIG2 file header is defined in ITU-T T.88, Annex D.4:
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// https://www.itu.int/rec/T-REC-T.88
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static stripFileHeader(bytes) {
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if (
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bytes.length >= 9 &&
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bytes[0] === 0x97 &&
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bytes[1] === 0x4a &&
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bytes[2] === 0x42 &&
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bytes[3] === 0x32 &&
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bytes[4] === 0x0d &&
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bytes[5] === 0x0a &&
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bytes[6] === 0x1a &&
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bytes[7] === 0x0a
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) {
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const headerLength = (bytes[8] & 2) === 0 ? 13 : 9;
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return bytes.subarray(headerLength);
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}
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return bytes;
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}
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async decodeImage(bytes, length, _decoderOptions) {
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if (this.eof) {
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return this.buffer;
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}
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bytes = Jbig2Stream.stripFileHeader(bytes || this.bytes);
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let globals = null;
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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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globals = Jbig2Stream.stripFileHeader(globalsStream.getBytes());
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}
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}
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this.buffer = await JBig2CCITTFaxImage.instance.decode(
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bytes,
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this.dict.get("Width"),
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this.dict.get("Height"),
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globals
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);
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this.bufferLength = this.buffer.length;
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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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