84de1e9a92
Note that no other image stream implements a special `getBytes` method, which makes `JpegStream` look somewhat odd.
I'm actually not sure what purpose this methods serves, since I successfully ran all tests locally with it commented out. Furhermore, I also ran tests with an added `if (length && length !== this.bufferLength) { throw new Error('length mismatch'); }` check, and didn't get a single test failure in that case either.
Looking at the history, it seems that this code originated back in PR 4528, but as far as I can tell there's no mention in either commit messages nor PR comments of why it was necessary to add a "special" `getBytes` function for the `JpegStream`.
My assumption is that there's a good reason why this method was added, e.g. to address a *specific* regression in one of the reference tests. However, I did check out commit 58f697f977 locally and ran tests with this method commented out, and there didn't seem to be any image-related failures in that case either!?
Hence I'm suggesting that we attempt to simplify this code slightly be removing this special `getBytes` method. However, please note that there's perhaps a *small* risk of regressions in an edge-case where we currently have insufficient test-coverage.
113 lines
3.8 KiB
JavaScript
113 lines
3.8 KiB
JavaScript
/* Copyright 2012 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.
|
|
*/
|
|
|
|
import { createObjectURL, shadow } from '../shared/util';
|
|
import { DecodeStream } from './stream';
|
|
import { isDict } from './primitives';
|
|
import { JpegImage } from './jpg';
|
|
|
|
/**
|
|
* Depending on the type of JPEG a JpegStream is handled in different ways. For
|
|
* JPEG's that are supported natively such as DeviceGray and DeviceRGB the image
|
|
* data is stored and then loaded by the browser. For unsupported JPEG's we use
|
|
* a library to decode these images and the stream behaves like all the other
|
|
* DecodeStreams.
|
|
*/
|
|
let JpegStream = (function JpegStreamClosure() {
|
|
function JpegStream(stream, maybeLength, dict, params) {
|
|
// Some images may contain 'junk' before the SOI (start-of-image) marker.
|
|
// Note: this seems to mainly affect inline images.
|
|
let ch;
|
|
while ((ch = stream.getByte()) !== -1) {
|
|
if (ch === 0xFF) { // Find the first byte of the SOI marker (0xFFD8).
|
|
stream.skip(-1); // Reset the stream position to the SOI.
|
|
break;
|
|
}
|
|
}
|
|
this.stream = stream;
|
|
this.maybeLength = maybeLength;
|
|
this.dict = dict;
|
|
this.params = params;
|
|
|
|
DecodeStream.call(this, maybeLength);
|
|
}
|
|
|
|
JpegStream.prototype = Object.create(DecodeStream.prototype);
|
|
|
|
Object.defineProperty(JpegStream.prototype, 'bytes', {
|
|
get: function JpegStream_bytes() {
|
|
// If `this.maybeLength` is null, we'll get the entire stream.
|
|
return shadow(this, 'bytes', this.stream.getBytes(this.maybeLength));
|
|
},
|
|
configurable: true,
|
|
});
|
|
|
|
JpegStream.prototype.ensureBuffer = function(requested) {
|
|
// No-op, since `this.readBlock` will always parse the entire image and
|
|
// directly insert all of its data into `this.buffer`.
|
|
};
|
|
|
|
JpegStream.prototype.readBlock = function() {
|
|
if (this.eof) {
|
|
return;
|
|
}
|
|
let jpegImage = new JpegImage();
|
|
|
|
// Checking if values need to be transformed before conversion.
|
|
let decodeArr = this.dict.getArray('Decode', 'D');
|
|
if (this.forceRGB && Array.isArray(decodeArr)) {
|
|
let bitsPerComponent = this.dict.get('BitsPerComponent') || 8;
|
|
let decodeArrLength = decodeArr.length;
|
|
let transform = new Int32Array(decodeArrLength);
|
|
let transformNeeded = false;
|
|
let maxValue = (1 << bitsPerComponent) - 1;
|
|
for (let i = 0; i < decodeArrLength; i += 2) {
|
|
transform[i] = ((decodeArr[i + 1] - decodeArr[i]) * 256) | 0;
|
|
transform[i + 1] = (decodeArr[i] * maxValue) | 0;
|
|
if (transform[i] !== 256 || transform[i + 1] !== 0) {
|
|
transformNeeded = true;
|
|
}
|
|
}
|
|
if (transformNeeded) {
|
|
jpegImage.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;
|
|
}
|
|
}
|
|
|
|
jpegImage.parse(this.bytes);
|
|
let data = jpegImage.getData(this.drawWidth, this.drawHeight,
|
|
this.forceRGB);
|
|
this.buffer = data;
|
|
this.bufferLength = data.length;
|
|
this.eof = true;
|
|
};
|
|
|
|
JpegStream.prototype.getIR = function(forceDataSchema = false) {
|
|
return createObjectURL(this.bytes, 'image/jpeg', forceDataSchema);
|
|
};
|
|
|
|
return JpegStream;
|
|
})();
|
|
|
|
export {
|
|
JpegStream,
|
|
};
|