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Merge pull request #8620 from Rob--W/issue-8560-improve-png-compression

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Improve compression of PNG images embedded in generated SVG files
This commit is contained in:
Yury Delendik 2017-07-14 07:23:38 -05:00 committed by GitHub
commit ca3c08f12b
9 changed files with 329 additions and 71 deletions
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38
examples/node/domstubs.js
View File

@ -41,24 +41,6 @@ function xmlEncode(s){
return buf;
}
global.btoa = function btoa(chars) {
var digits =
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
var buffer = '';
var i, n;
for (i = 0, n = chars.length; i < n; i += 3) {
var b1 = chars.charCodeAt(i) & 0xFF;
var b2 = chars.charCodeAt(i + 1) & 0xFF;
var b3 = chars.charCodeAt(i + 2) & 0xFF;
var d1 = b1 >> 2, d2 = ((b1 & 3) << 4) | (b2 >> 4);
var d3 = i + 1 < n ? ((b2 & 0xF) << 2) | (b3 >> 6) : 64;
var d4 = i + 2 < n ? (b3 & 0x3F) : 64;
buffer += (digits.charAt(d1) + digits.charAt(d2) +
digits.charAt(d3) + digits.charAt(d4));
}
return buffer;
};
function DOMElement(name) {
this.nodeName = name;
this.childNodes = [];
@ -127,7 +109,7 @@ DOMElement.prototype = {
},
}
global.document = {
const document = {
childNodes : [],
get currentScript() {
@ -171,4 +153,20 @@ Image.prototype = {
}
}
global.Image = Image;
exports.document = document;
exports.Image = Image;
var exported_symbols = Object.keys(exports);
exports.setStubs = function(namespace) {
exported_symbols.forEach(function(key) {
console.assert(!(key in namespace), 'property should not be set: ' + key);
namespace[key] = exports[key];
});
};
exports.unsetStubs = function(namespace) {
exported_symbols.forEach(function(key) {
console.assert(key in namespace, 'property should be set: ' + key);
delete namespace[key];
});
};

2
examples/node/pdf2svg.js
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@ -8,7 +8,7 @@
var fs = require('fs');
// HACK few hacks to let PDF.js be loaded not as a module in global space.
require('./domstubs.js');
require('./domstubs.js').setStubs(global);
// Run `gulp dist-install` to generate 'pdfjs-dist' npm package files.
var pdfjsLib = require('pdfjs-dist');

1
gulpfile.js
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@ -1044,6 +1044,7 @@ gulp.task('lib', ['buildnumber'], function () {
'src/{pdf,pdf.worker}.js',
], { base: 'src/', }),
gulp.src([
'examples/node/domstubs.js',
'web/*.js',
'!web/pdfjs.js',
'!web/viewer.js',

124
src/display/svg.js
View File

@ -12,10 +12,11 @@
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* globals __non_webpack_require__ */
import {
createObjectURL, FONT_IDENTITY_MATRIX, IDENTITY_MATRIX, ImageKind, isArray,
isNum, OPS, Util, warn
isNodeJS, isNum, OPS, Util, warn
} from '../shared/util';
var SVGGraphics = function() {
@ -97,6 +98,89 @@ var convertImgDataToPng = (function convertImgDataToPngClosure() {
return (b << 16) | a;
}
/**
* @param {Uint8Array} literals The input data.
* @returns {Uint8Array} The DEFLATE-compressed data stream in zlib format.
* This is the required format for compressed streams in the PNG format:
* http://www.libpng.org/pub/png/spec/1.2/PNG-Compression.html
*/
function deflateSync(literals) {
if (!isNodeJS()) {
// zlib is certainly not available outside of Node.js. We can either use
// the pako library for client-side DEFLATE compression, or use the canvas
// API of the browser to obtain a more optimal PNG file.
return deflateSyncUncompressed(literals);
}
try {
// NOTE: This implementation is far from perfect, but already way better
// than not applying any compression.
//
// A better algorithm will try to choose a good predictor/filter and
// then choose a suitable zlib compression strategy (e.g. 3,Z_RLE).
//
// Node v0.11.12 zlib.deflateSync is introduced (and returns a Buffer).
// Node v3.0.0 Buffer inherits from Uint8Array.
// Node v8.0.0 zlib.deflateSync accepts Uint8Array as input.
var input;
// eslint-disable-next-line no-undef
if (parseInt(process.versions.node) >= 8) {
input = literals;
} else {
// eslint-disable-next-line no-undef
input = new Buffer(literals);
}
var output = __non_webpack_require__('zlib')
.deflateSync(input, { level: 9, });
return output instanceof Uint8Array ? output : new Uint8Array(output);
} catch (e) {
warn('Not compressing PNG because zlib.deflateSync is unavailable: ' + e);
}
return deflateSyncUncompressed(literals);
}
// An implementation of DEFLATE with compression level 0 (Z_NO_COMPRESSION).
function deflateSyncUncompressed(literals) {
var len = literals.length;
var maxBlockLength = 0xFFFF;
var deflateBlocks = Math.ceil(len / maxBlockLength);
var idat = new Uint8Array(2 + len + deflateBlocks * 5 + 4);
var pi = 0;
idat[pi++] = 0x78; // compression method and flags
idat[pi++] = 0x9c; // flags
var pos = 0;
while (len > maxBlockLength) {
// writing non-final DEFLATE blocks type 0 and length of 65535
idat[pi++] = 0x00;
idat[pi++] = 0xff;
idat[pi++] = 0xff;
idat[pi++] = 0x00;
idat[pi++] = 0x00;
idat.set(literals.subarray(pos, pos + maxBlockLength), pi);
pi += maxBlockLength;
pos += maxBlockLength;
len -= maxBlockLength;
}
// writing non-final DEFLATE blocks type 0
idat[pi++] = 0x01;
idat[pi++] = len & 0xff;
idat[pi++] = len >> 8 & 0xff;
idat[pi++] = (~len & 0xffff) & 0xff;
idat[pi++] = (~len & 0xffff) >> 8 & 0xff;
idat.set(literals.subarray(pos), pi);
pi += literals.length - pos;
var adler = adler32(literals, 0, literals.length); // checksum
idat[pi++] = adler >> 24 & 0xff;
idat[pi++] = adler >> 16 & 0xff;
idat[pi++] = adler >> 8 & 0xff;
idat[pi++] = adler & 0xff;
return idat;
}
function encode(imgData, kind, forceDataSchema) {
var width = imgData.width;
var height = imgData.height;
@ -162,43 +246,7 @@ var convertImgDataToPng = (function convertImgDataToPngClosure() {
0x00 // interlace method
]);
var len = literals.length;
var maxBlockLength = 0xFFFF;
var deflateBlocks = Math.ceil(len / maxBlockLength);
var idat = new Uint8Array(2 + len + deflateBlocks * 5 + 4);
var pi = 0;
idat[pi++] = 0x78; // compression method and flags
idat[pi++] = 0x9c; // flags
var pos = 0;
while (len > maxBlockLength) {
// writing non-final DEFLATE blocks type 0 and length of 65535
idat[pi++] = 0x00;
idat[pi++] = 0xff;
idat[pi++] = 0xff;
idat[pi++] = 0x00;
idat[pi++] = 0x00;
idat.set(literals.subarray(pos, pos + maxBlockLength), pi);
pi += maxBlockLength;
pos += maxBlockLength;
len -= maxBlockLength;
}
// writing non-final DEFLATE blocks type 0
idat[pi++] = 0x01;
idat[pi++] = len & 0xff;
idat[pi++] = len >> 8 & 0xff;
idat[pi++] = (~len & 0xffff) & 0xff;
idat[pi++] = (~len & 0xffff) >> 8 & 0xff;
idat.set(literals.subarray(pos), pi);
pi += literals.length - pos;
var adler = adler32(literals, 0, literals.length); // checksum
idat[pi++] = adler >> 24 & 0xff;
idat[pi++] = adler >> 16 & 0xff;
idat[pi++] = adler >> 8 & 0xff;
idat[pi++] = adler & 0xff;
var idat = deflateSync(literals);
// PNG will consists: header, IHDR+data, IDAT+data, and IEND.
var pngLength = PNG_HEADER.length + (CHUNK_WRAPPER_SIZE * 3) +

1
test/pdfs/.gitignore vendored
View File

@ -288,3 +288,4 @@
!font_ascent_descent.pdf
!issue8097_reduced.pdf
!transparent.pdf
!xobject-image.pdf

61
test/pdfs/xobject-image.pdf Normal file
View File

@ -0,0 +1,61 @@
%PDF-1.1
1 0 obj
<</Type/Catalog/Pages 2 0 R>>
endobj
2 0 obj
<</Type/Pages/Count 1/Kids[3 0 R]/MediaBox [0 0 200 100]>>
endobj
3 0 obj
<<
/Type/Page
/Parent 2 0 R
/Resources <<
/XObject << /SomeImage 4 0 R >>
>>
/Contents 5 0 R
>>
endobj
4 0 obj
<<
/Type/XObject
/Subtype/Image
/Width 200 % The width or height directly affects the image's file size.
/Height 100
/ColorSpace/DeviceRGB
/DecodeParms [] % Forces NativeImageDecoder.isSupported to return false.
/BitsPerComponent 8
/Length 580
/Filter [ /ASCIIHexDecode /DCTDecode ]
>>
% convert -size 1x1 xc:red jpeg:- | xxd -p -c40
stream
ffd8ffe000104a46494600010100000100010000ffdb004300030202020202030202020303030304
060404040404080606050609080a0a090809090a0c0f0c0a0b0e0b09090d110d0e0f101011100a0c
12131210130f101010ffdb00430103030304030408040408100b090b101010101010101010101010
1010101010101010101010101010101010101010101010101010101010101010101010101010ffc0
0011080001000103011100021101031101ffc40014000100000000000000000000000000000008ff
c40014100100000000000000000000000000000000ffc40015010101000000000000000000000000
00000709ffc40014110100000000000000000000000000000000ffda000c03010002110311003f00
3a03154dffd9
endstream
endobj
5 0 obj
<</Length 14>>
stream
500 0 0 400 0 0 cm
/SomeImage Do
endstream
endobj
xref
0 6
0000000000 65535 f
0000000008 00000 n
0000000054 00000 n
0000000128 00000 n
0000000246 00000 n
0000001201 00000 n
trailer
<</Root 1 0 R/Size 6>>
startxref
1281
%%EOF

1
test/unit/clitests.json
View File

@ -7,6 +7,7 @@
"cff_parser_spec.js",
"cmap_spec.js",
"crypto_spec.js",
"display_svg_spec.js",
"document_spec.js",
"dom_utils_spec.js",
"evaluator_spec.js",

135
test/unit/display_svg_spec.js Normal file
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@ -0,0 +1,135 @@
/* Copyright 2017 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.
*/
/* globals __non_webpack_require__ */
import { isNodeJS, NativeImageDecoding } from '../../src/shared/util';
import { setStubs, unsetStubs } from '../../examples/node/domstubs';
import { buildGetDocumentParams } from './test_utils';
import { getDocument } from '../../src/display/api';
import { SVGGraphics } from '../../src/display/svg';
// withZlib(true, callback); = run test with require('zlib') if possible.
// withZlib(false, callback); = run test without require('zlib').deflateSync.
// The return value of callback is returned as-is.
function withZlib(isZlibRequired, callback) {
if (isZlibRequired) {
// We could try to polyfill zlib in the browser, e.g. using pako.
// For now, only support zlib functionality on Node.js
if (!isNodeJS()) {
throw new Error('zlib test can only be run in Node.js');
}
return callback();
}
if (!isNodeJS()) {
// Assume that require('zlib') is unavailable in non-Node.
return callback();
}
var zlib = __non_webpack_require__('zlib');
var deflateSync = zlib.deflateSync;
zlib.deflateSync = function() {
throw new Error('zlib.deflateSync is explicitly disabled for testing.');
};
try {
return callback();
} finally {
zlib.deflateSync = deflateSync;
}
}
describe('SVGGraphics', function () {
var loadingTask;
var page;
beforeAll(function(done) {
loadingTask = getDocument(buildGetDocumentParams('xobject-image.pdf', {
nativeImageDecoderSupport: NativeImageDecoding.DISPLAY,
}));
loadingTask.promise.then(function(doc) {
doc.getPage(1).then(function(firstPage) {
page = firstPage;
done();
});
});
});
afterAll(function(done) {
loadingTask.destroy().then(done);
});
describe('paintImageXObject', function() {
function getSVGImage() {
var svgGfx;
return page.getOperatorList().then(function(opList) {
var forceDataSchema = true;
svgGfx = new SVGGraphics(page.commonObjs, page.objs, forceDataSchema);
return svgGfx.loadDependencies(opList);
}).then(function() {
var svgImg;
// A mock to steal the svg:image element from paintInlineImageXObject.
var elementContainer = {
appendChild(element) {
svgImg = element;
},
};
// This points to the XObject image in xobject-image.pdf.
var xobjectObjId = { ref: 4, gen: 0, };
if (isNodeJS()) {
setStubs(global);
}
try {
svgGfx.paintImageXObject(xobjectObjId, elementContainer);
} finally {
if (isNodeJS()) {
unsetStubs(global);
}
}
return svgImg;
});
}
it('should produce a reasonably small svg:image', function() {
if (!isNodeJS()) {
pending('zlib.deflateSync is not supported in non-Node environments.');
}
withZlib(true, getSVGImage).then(function(svgImg) {
expect(svgImg.nodeName).toBe('svg:image');
expect(svgImg.getAttribute('width')).toBe('200px');
expect(svgImg.getAttribute('height')).toBe('100px');
var imgUrl = svgImg.getAttribute('xlink:href');
// forceDataSchema = true, so the generated URL should be a data:-URL.
expect(imgUrl).toMatch(/^data:image\/png;base64,/);
// Test whether the generated image has a reasonable file size.
// I obtained a data URL of size 366 with Node 8.1.3 and zlib 1.2.11.
// Without zlib (uncompressed), the size of the data URL was excessive
// (80247).
expect(imgUrl.length).toBeLessThan(367);
});
});
it('should produce a svg:image even if zlib is unavailable', function() {
withZlib(false, getSVGImage).then(function(svgImg) {
expect(svgImg.nodeName).toBe('svg:image');
expect(svgImg.getAttribute('width')).toBe('200px');
expect(svgImg.getAttribute('height')).toBe('100px');
var imgUrl = svgImg.getAttribute('xlink:href');
expect(imgUrl).toMatch(/^data:image\/png;base64,/);
// The size of our naively generated PNG file is excessive :(
expect(imgUrl.length).toBe(80247);
});
});
});
});

37
test/unit/jasmine-boot.js
View File

@ -42,18 +42,31 @@
function initializePDFJS(callback) {
Promise.all([
'pdfjs/display/global', 'pdfjs-test/unit/annotation_spec',
'pdfjs-test/unit/api_spec', 'pdfjs-test/unit/bidi_spec',
'pdfjs-test/unit/cff_parser_spec', 'pdfjs-test/unit/cmap_spec',
'pdfjs-test/unit/crypto_spec', 'pdfjs-test/unit/custom_spec',
'pdfjs-test/unit/document_spec', 'pdfjs-test/unit/dom_utils_spec',
'pdfjs-test/unit/evaluator_spec', 'pdfjs-test/unit/fonts_spec',
'pdfjs-test/unit/function_spec', 'pdfjs-test/unit/metadata_spec',
'pdfjs-test/unit/murmurhash3_spec', 'pdfjs-test/unit/network_spec',
'pdfjs-test/unit/parser_spec', 'pdfjs-test/unit/primitives_spec',
'pdfjs-test/unit/stream_spec', 'pdfjs-test/unit/type1_parser_spec',
'pdfjs-test/unit/ui_utils_spec', 'pdfjs-test/unit/unicode_spec',
'pdfjs-test/unit/util_spec', 'pdfjs-test/unit/util_stream_spec'
'pdfjs/display/global',
'pdfjs-test/unit/annotation_spec',
'pdfjs-test/unit/api_spec',
'pdfjs-test/unit/bidi_spec',
'pdfjs-test/unit/cff_parser_spec',
'pdfjs-test/unit/cmap_spec',
'pdfjs-test/unit/crypto_spec',
'pdfjs-test/unit/custom_spec',
'pdfjs-test/unit/display_svg_spec',
'pdfjs-test/unit/document_spec',
'pdfjs-test/unit/dom_utils_spec',
'pdfjs-test/unit/evaluator_spec',
'pdfjs-test/unit/fonts_spec',
'pdfjs-test/unit/function_spec',
'pdfjs-test/unit/metadata_spec',
'pdfjs-test/unit/murmurhash3_spec',
'pdfjs-test/unit/network_spec',
'pdfjs-test/unit/parser_spec',
'pdfjs-test/unit/primitives_spec',
'pdfjs-test/unit/stream_spec',
'pdfjs-test/unit/type1_parser_spec',
'pdfjs-test/unit/ui_utils_spec',
'pdfjs-test/unit/unicode_spec',
'pdfjs-test/unit/util_spec',
'pdfjs-test/unit/util_stream_spec',
].map(function (moduleName) {
return SystemJS.import(moduleName);
})).then(function (modules) {