fd03cd5493
We introduced the use of OffscreenCanvas in #14754 and this patch aims to use them for all kind of images. It'll slightly improve performances (and maybe slightly decrease memory use). Since an image can be rendered in using some transfer maps but because of OffscreenCanvas we don't have the underlying pixels array the transfer maps stuff is re-implemented in using the SVG filter feComponentTransfer.
107 lines
3.4 KiB
JavaScript
107 lines
3.4 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 { DecodeStream } from "./decode_stream.js";
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import { Dict } from "./primitives.js";
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import { JpegImage } from "./jpg.js";
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import { shadow } from "../shared/util.js";
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/**
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* For JPEG's we use a library to decode these images and the stream behaves
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* like all the other DecodeStreams.
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*/
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class JpegStream extends DecodeStream {
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constructor(stream, maybeLength, 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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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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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("D", "Decode");
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if ((this.forceRGBA || this.forceRGB) && Array.isArray(decodeArr)) {
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const bitsPerComponent = this.dict.get("BPC", "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 (this.params instanceof Dict) {
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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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forceRGBA: this.forceRGBA,
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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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}
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export { JpegStream };
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