9e262ae7fa
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120 lines
4.0 KiB
JavaScript
120 lines
4.0 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 { createObjectURL, shadow } from "../shared/util.js";
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import { DecodeStream } from "./stream.js";
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import { isDict } from "./primitives.js";
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import { JpegImage } from "./jpg.js";
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/**
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* Depending on the type of JPEG a JpegStream is handled in different ways. For
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* JPEG's that are supported natively such as DeviceGray and DeviceRGB the image
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* data is stored and then loaded by the browser. For unsupported JPEG's we use
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* a library to decode these images and the stream behaves like all the other
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* DecodeStreams.
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*/
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const JpegStream = (function JpegStreamClosure() {
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function JpegStream(stream, maybeLength, dict, params) {
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// Some images may contain 'junk' before the SOI (start-of-image) marker.
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// Note: this seems to mainly affect inline images.
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let ch;
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while ((ch = stream.getByte()) !== -1) {
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// Find the first byte of the SOI marker (0xFFD8).
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if (ch === 0xff) {
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stream.skip(-1); // Reset the stream position to the SOI.
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break;
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}
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}
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this.stream = stream;
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this.maybeLength = maybeLength;
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this.dict = dict;
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this.params = params;
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DecodeStream.call(this, maybeLength);
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}
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JpegStream.prototype = Object.create(DecodeStream.prototype);
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Object.defineProperty(JpegStream.prototype, "bytes", {
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get: function JpegStream_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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configurable: true,
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});
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JpegStream.prototype.ensureBuffer = function(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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JpegStream.prototype.readBlock = function() {
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if (this.eof) {
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return;
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}
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const jpegOptions = {
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decodeTransform: undefined,
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colorTransform: undefined,
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};
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// Checking if values need to be transformed before conversion.
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const decodeArr = this.dict.getArray("Decode", "D");
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if (this.forceRGB && Array.isArray(decodeArr)) {
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const bitsPerComponent = this.dict.get("BitsPerComponent") || 8;
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const decodeArrLength = decodeArr.length;
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const transform = new Int32Array(decodeArrLength);
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let transformNeeded = false;
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const maxValue = (1 << bitsPerComponent) - 1;
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for (let i = 0; i < decodeArrLength; i += 2) {
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transform[i] = ((decodeArr[i + 1] - decodeArr[i]) * 256) | 0;
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transform[i + 1] = (decodeArr[i] * maxValue) | 0;
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if (transform[i] !== 256 || transform[i + 1] !== 0) {
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transformNeeded = true;
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}
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}
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if (transformNeeded) {
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jpegOptions.decodeTransform = transform;
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}
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}
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// Fetching the 'ColorTransform' entry, if it exists.
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if (isDict(this.params)) {
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const colorTransform = this.params.get("ColorTransform");
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if (Number.isInteger(colorTransform)) {
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jpegOptions.colorTransform = colorTransform;
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}
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}
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const jpegImage = new JpegImage(jpegOptions);
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jpegImage.parse(this.bytes);
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const data = jpegImage.getData({
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width: this.drawWidth,
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height: this.drawHeight,
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forceRGB: this.forceRGB,
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isSourcePDF: true,
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});
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this.buffer = data;
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this.bufferLength = data.length;
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this.eof = true;
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};
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JpegStream.prototype.getIR = function(forceDataSchema = false) {
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return createObjectURL(this.bytes, "image/jpeg", forceDataSchema);
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};
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return JpegStream;
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})();
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export { JpegStream };
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