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Add a new parameter to JpegImage.getData to indicate the source of the image data (issue 9513)

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The purpose of this patch is to provide a better default behaviour when `JpegImage` is used to parse standalone JPEG images with CMYK colour spaces.
Since the issue that the patch concerns is somewhat of a special-case, the implementation utilizes the already existing decode support in an attempt to minimize the impact w.r.t. code size.

*Please note:* It's always possible for the user of `JpegImage` to control image inversion, and thus override the new behaviour, by simply passing a custom `decodeTransform` array upon initialization.
This commit is contained in:
Jonas Jenwald 2018-09-02 13:55:27 +02:00
parent 47bf12cbac
commit 663922f93f
3 changed files with 36 additions and 11 deletions
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33
src/core/jpg.js
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@ -975,7 +975,7 @@ var JpegImage = (function JpegImageClosure() {
this.numComponents = this.components.length;
},
_getLinearizedBlockData: function getLinearizedBlockData(width, height) {
_getLinearizedBlockData(width, height, isSourcePDF = false) {
var scaleX = this.width / width, scaleY = this.height / height;
var component, componentScaleX, componentScaleY, blocksPerScanline;
@ -1013,7 +1013,24 @@ var JpegImage = (function JpegImageClosure() {
}
// decodeTransform contains pairs of multiplier (-256..256) and additive
const transform = this._decodeTransform;
let transform = this._decodeTransform;
// In PDF files, JPEG images with CMYK colour spaces are usually inverted
// (this can be observed by extracting the raw image data).
// Since the conversion algorithms (see below) were written primarily for
// the PDF use-cases, attempting to use `JpegImage` to parse standalone
// JPEG (CMYK) images may thus result in inverted images (see issue 9513).
//
// Unfortunately it's not (always) possible to tell, from the image data
// alone, if it needs to be inverted. Thus in an attempt to provide better
// out-of-box behaviour when `JpegImage` is used standalone, default to
// inverting JPEG (CMYK) images if and only if the image data does *not*
// come from a PDF file and no `decodeTransform` was passed by the user.
if (!transform && numComponents === 4 && !isSourcePDF) {
transform = new Int32Array([
-256, 255, -256, 255, -256, 255, -256, 255]);
}
if (transform) {
for (i = 0; i < dataLength;) {
for (j = 0, k = 0; j < numComponents; j++, i++, k += 2) {
@ -1162,14 +1179,14 @@ var JpegImage = (function JpegImageClosure() {
return data.subarray(0, offset);
},
getData: function getData(width, height, forceRGBoutput) {
getData({ width, height, forceRGB = false, isSourcePDF = false, }) {
if (this.numComponents > 4) {
throw new JpegError('Unsupported color mode');
}
// type of data: Uint8Array(width * height * numComponents)
var data = this._getLinearizedBlockData(width, height);
// Type of data: Uint8ClampedArray(width * height * numComponents)
var data = this._getLinearizedBlockData(width, height, isSourcePDF);
if (this.numComponents === 1 && forceRGBoutput) {
if (this.numComponents === 1 && forceRGB) {
var dataLength = data.length;
var rgbData = new Uint8ClampedArray(dataLength * 3);
var offset = 0;
@ -1184,11 +1201,11 @@ var JpegImage = (function JpegImageClosure() {
return this._convertYccToRgb(data);
} else if (this.numComponents === 4) {
if (this._isColorConversionNeeded) {
if (forceRGBoutput) {
if (forceRGB) {
return this._convertYcckToRgb(data);
}
return this._convertYcckToCmyk(data);
} else if (forceRGBoutput) {
} else if (forceRGB) {
return this._convertCmykToRgb(data);
}
}