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bv7_jpeg2array_b

jpeg -> array

目前为 2018-02-20 提交的版本。查看 最新版本。

此脚本不应直接安装，它是一个供其他脚本使用的外部库。如果您需要使用该库，请在脚本元属性加入：// @require https://update.cn-greasyfork.org/scripts/38665/252976/bv7_jpeg2array_b.js 

  1. // ==UserScript==
  2. // @name         bv7_jpeg2array_b
  3. // @namespace    bv7
  4. // @version      0.3
  5. // @description  jpeg -> array
  6. // @author       bv7
  7. // @grant        GM_xmlhttpRequest
  8. // ==/UserScript==
  9.  
  10. class BaseImage {
  11. 	load(url, onload) {
  12. 		GM_xmlhttpRequest({
  13. 			method          : 'GET',
  14. 			url             : this.nodesCaptchaImgs[iImg].src,
  15. 			overrideMimeType: 'text/plain; charset=x-user-defined',
  16. 			onload          : (v) => {
  17. 				this.data = v.responseText;
  18. 				this.seek(0);
  19. 				if (onload) onload(v);
  20. 			}
  21. 		});		
  22. 	}
  23. 	seek(iData = 0) {
  24. 		this.iData = iData;
  25. 	}
  26. 	skip(i) {
  27. 		this.iData +=i;
  28. 	}
  29. 	getUint8() {
  30. 		return this.iData < this.data.length ? this.data.charCodeAt(this.iData) && 0xff : 0;
  31. 	}
  32. 	readUint8() {
  33. 		return this.iData < this.data.length ? this.data.charCodeAt(this.iData++) && 0xff : 0;
  34. 	}
  35. 	readUint16() {
  36. 		return (this.readUint8() << 8) | this.readUint8();
  37. 	}
  38. }
  39.  
  40.  
  41. class JpegImage extends BaseImage {
  42. 	constructor() {
  43. 		this.dctZigZag = new Int32Array([
  44. 			 0,
  45. 			 1,  8,
  46. 			16,  9,  2,
  47. 			 3, 10, 17, 24,
  48. 			32, 25, 18, 11, 4,
  49. 			 5, 12, 19, 26, 33, 40,
  50. 			48, 41, 34, 27, 20, 13,  6,
  51. 			 7, 14, 21, 28, 35, 42, 49, 56,
  52. 			57, 50, 43, 36, 29, 22, 15,
  53. 			23, 30, 37, 44, 51, 58,
  54. 			59, 52, 45, 38, 31,
  55. 			39, 46, 53, 60,
  56. 			61, 54, 47,
  57. 			55, 62,
  58. 			63
  59. 		]);
  60. 		this.dctCos1  =  4017   // cos(pi/16)
  61. 		this.dctSin1  =   799   // sin(pi/16)
  62. 		this.dctCos3  =  3406   // cos(3*pi/16)
  63. 		this.dctSin3  =  2276   // sin(3*pi/16)
  64. 		this.dctCos6  =  1567   // cos(6*pi/16)
  65. 		this.dctSin6  =  3784   // sin(6*pi/16)
  66. 		this.dctSqrt2 =  5793   // sqrt(2)
  67. 		this.dctSqrt1d2 = 2896  // sqrt(2) / 2
  68. 	}
  69. 	readDataBlock() {
  70. 		value = new Array(this.readUint16() - 2);
  71. 		value.forEach((v, i) => value[i] = this.readUint8());
  72. 		return value;
  73. 	}
  74. 	seekBit() {
  75. 		this.bitsData  = 0;
  76. 		this.bitsCount = 0;
  77. 	}
  78. 	readBit() {
  79. 		if (this.bitsCount > 0) this.bitsCount--;
  80. 		else {
  81. 			this.bitsData = this.readUint8();
  82. 			if (this.bitsData == 0xFF) {
  83. 				let nextByte = this.readUint8();
  84. 				if (nextByte) {
  85. 					console.log('JpegImage: Error: unexpected marker: ' + ((this.bitsData << 8) | nextByte).toString(16));
  86. 					return;
  87. 				}
  88. 				// unstuff 0
  89. 			}
  90. 			this.bitsCount = 7;
  91. 		}
  92. 		return (this.bitsData >> this.bitsCount) & 1;
  93. 	}
  94. 	prepareComponents(frame) {
  95. 		frame.maxH = 0;
  96. 		frame.maxV = 0;
  97. 		frame.componentsOrder.forEach((v) => {
  98. 			let component = frame.components[v];
  99. 			if (frame.maxH < component.h) frame.maxH = component.h;
  100. 			if (frame.maxV < component.v) frame.maxV = component.v;
  101. 		});
  102. 		frame.mcusPerLine   = Math.ceil(frame.samplesPerLine / 8 / maxH);
  103. 		frame.mcusPerColumn = Math.ceil(frame.scanLines      / 8 / maxV);
  104. 		frame.componentsOrder.forEach((v) => {
  105. 			let component = frame.components[v];
  106.             component.blocksPerLine   = Math.ceil(Math.ceil(frame.samplesPerLine / 8) * component.h / maxH);
  107.             component.blocksPerColumn = Math.ceil(Math.ceil(frame.scanLines      / 8) * component.v / maxV);
  108. 			component.blocks          = [];
  109. 			let blocksPerLineForMcu   = mcusPerLine   * component.h;
  110. 			let blocksPerColumnForMcu = mcusPerColumn * component.v;
  111. 			for (let i = 0; i < blocksPerColumnForMcu; i++) {
  112. 				let row = [];
  113. 				for (let j = 0; j < blocksPerLineForMcu; j++) row.push(new Int32Array(64));
  114. 				component.blocks.push(row);
  115.             }
  116. 		});
  117. 	}
  118. 	buildHuffmanTable(codeLengths, values) {
  119. 		let length = codeLengths.length;
  120. 		while (length > 0 && !codeLengths[length - 1]) length--;
  121. 		let p = {children: [], index: 0};
  122. 		let code = [p];
  123. 		for (let i = 0, k = 0, q; i < length; i++) {
  124. 			for (let j = 0; j < codeLengths[i]; j++, k++) {
  125. 				p = code.pop();
  126. 				p.children[p.index] = values[k];
  127. 				while (p.index > 0) p = code.pop();
  128. 				p.index++;
  129. 				code.push(p);
  130. 				while (code.length <= i) {
  131. 					code.push(q = {children: [], index: 0});
  132. 					p.children[p.index] = q.children;
  133. 					p = q;
  134. 				}
  135. 			}
  136. 			if (i + 1 < length) { // p here points to last code
  137. 				code.push(q = {children: [], index: 0});
  138. 				p.children[p.index] = q.children;
  139. 				p = q;
  140. 			}
  141. 		}
  142. 		return code[0].children;
  143. 	}
  144. 	decodeScan(data, frame, components, resetInterval, spectralStart, spectralEnd, successivePrev, successive) {
  145. 		this.seekBit();
  146. 		let decodeHuffman = (tree) => {
  147. 			let node = tree;
  148. 			let bit;
  149. 			while ((bit = this.readBit()) !== null) {
  150. 				node = node[bit];
  151. 				if (typeof node === 'number') return node;
  152. 				if (typeof node !== 'object') {
  153. 					console.log('JpegImage: Error: invalid huffman sequence');
  154. 					return;
  155. 				}
  156. 			}
  157. 			return null;
  158. 		};
  159. 		let receive = (length) => {
  160. 			let n = 0;
  161. 			for (; length > 0; length--) {
  162. 				let bit = this.readBit();
  163. 				if (bit === null) return;
  164. 				n = (n << 1) | bit;
  165. 			}
  166. 			return n;
  167. 		};
  168. 		let receiveAndExtend = (length) => {
  169. 			let n = receive(length);
  170. 			return (n >= 1 << (length - 1)) ? n : (n + (-1 << length) + 1);
  171. 		};
  172. 		let decodeBaseline = (component, zz) => {
  173. 			let t = decodeHuffman(component.huffmanTableDC);
  174. 			let diff = t === 0 ? 0 : receiveAndExtend(t);
  175. 			zz[0] = (component.pred += diff);
  176. 			let k = 1;
  177. 			while (k < 64) {
  178. 				let rs = decodeHuffman(component.huffmanTableAC);
  179. 				let s  = rs & 15;
  180. 				let r  = rs >> 4;
  181. 				if (s === 0) {
  182. 					if (r < 15) break;
  183. 					else {
  184. 						k += 16;
  185. 						continue;
  186. 					}
  187. 				} else {
  188. 					k += r;
  189. 					zz[dctZigZag[k]] = receiveAndExtend(s);
  190. 					k++;
  191. 				}
  192. 			}
  193. 		}
  194. 		let decodeDCFirst = (component, zz) => {
  195. 			let t    = decodeHuffman(component.huffmanTableDC);
  196. 			let diff = t === 0 ? 0 : (receiveAndExtend(t) << successive);
  197. 			zz[0]    = (component.pred += diff);
  198. 		}
  199. 		let decodeDCSuccessive = (component, zz) => zz[0] |= this.readBit() << successive;
  200. 		let eobrun = 0;
  201. 		let decodeACFirst = (component, zz) => {
  202. 			if (eobrun > 0) eobrun--;
  203. 			else {
  204. 				let k = spectralStart;
  205. 				while (k <= spectralEnd) {
  206. 					let rs = decodeHuffman(component.huffmanTableAC);
  207. 					let s  = rs & 15;
  208. 					let r  = rs >> 4;
  209. 					if (s === 0) {
  210. 						if (r < 15) {
  211. 							eobrun = receive(r) + (1 << r) - 1;
  212. 							break;
  213. 						} else k += 16;
  214. 					} else {
  215. 						k += r;
  216. 						let z = ;
  217. 						zz[this.dctZigZag[k]] = receiveAndExtend(s) * (1 << successive);
  218. 						k++;
  219. 					}
  220. 				}
  221. 			}
  222. 		};
  223. 		let successiveACState     = 0;
  224. 		let successiveACNextValue = 0;
  225. 		let decodeACSuccessive = (component, zz) => {
  226. 			let k = spectralStart;
  227. 			let r = 0;
  228. 			while(k <= spectralEnd) {
  229. 				let z         = dctZigZag[k];
  230. 				let direction = zz[z] < 0 ? -1 : 1;
  231. 				switch (successiveACState) {
  232. 					case 0: // initial state
  233. 						let rs = decodeHuffman(component.huffmanTableAC);
  234. 						let s  = rs & 15;
  235. 						r = rs >> 4;
  236. 						if (s === 0) {
  237. 							if (r < 15) {
  238. 								eobrun            = receive(r) + (1 << r);
  239. 								successiveACState = 4;
  240. 							} else {
  241. 								r = 16;
  242. 								successiveACState = 1;
  243. 							}
  244. 						} else if (s !== 1) {
  245. 							console.log('JpegImage: Error: invalid ACn encoding');
  246. 							return;
  247. 						} else {
  248. 							successiveACNextValue = receiveAndExtend(s);
  249. 							successiveACState     = r ? 2 : 3;
  250. 						}
  251. 						continue;
  252. 					case 1: // skipping r zero items
  253. 					case 2:
  254. 						if (zz[z]) zz[z] += (this.readBit() << successive) * direction;
  255. 						else {
  256. 							r--;
  257. 							if (r === 0) successiveACState = successiveACState == 2 ? 3 : 0;
  258. 						}
  259. 						break;
  260. 					case 3: // set value for a zero item
  261. 						if (zz[z]) zz[z] += (this.readBit() << successive) * direction;
  262. 						else {
  263. 							zz[z]             = successiveACNextValue << successive;
  264. 							successiveACState = 0;
  265. 						}
  266. 						break;
  267. 					case 4: // eob
  268. 						if (zz[z]) zz[z] += (this.readBit() << successive) * direction;
  269. 						break;
  270. 				}
  271. 				k++;
  272. 			}
  273. 			if (successiveACState === 4) {
  274. 				eobrun--;
  275. 				if (eobrun === 0) successiveACState = 0;
  276. 			}
  277. 		};
  278. 		let decodeMcu = (component, decode, mcu, row, col) => decode(
  279. 			component,
  280. 			component.blocks[((mcu / frame.mcusPerLine) | 0) * component.v + row][(mcu % frame.mcusPerLine) * component.h + col]
  281. 		);
  282. 		let decodeBlock = (component, decode, mcu) => decode(
  283. 			component,
  284. 			component.blocks[(mcu / component.blocksPerLine) | 0][mcu % component.blocksPerLine]
  285. 		);
  286. 		let decodeFn = frame.progressive ? (
  287. 			spectralStart === 0 ? (
  288. 				successivePrev === 0 ? decodeDCFirst : decodeDCSuccessive
  289. 			) : (
  290. 				successivePrev === 0 ? decodeACFirst : decodeACSuccessive
  291. 			)
  292. 		) : decodeBaseline;
  293. 		let mcu         = 0;
  294. 		let mcuExpected = (components.length == 1) ? (
  295. 			components[0].blocksPerLine * components[0].blocksPerColumn
  296. 		) : (
  297. 			frame.mcusPerLine * frame.mcusPerColumn
  298. 		);
  299. 		if (!resetInterval) resetInterval = mcuExpected;
  300. 		while (mcu < mcuExpected) {
  301. 			// reset interval stuff
  302. 			components.forEach((v) => v.pred = 0);
  303. 			eobrun = 0;
  304. 			if (components.length == 1) {
  305. 				let component = components[0];
  306. 				for (let n = 0; n < resetInterval; n++, mcu++) decodeBlock(component, decodeFn, mcu);
  307. 			} else for (let n = 0; n < resetInterval; n++) {
  308. 				for (let i = 0; i < components.length; i++) {
  309. 					let component = components[i];
  310. 					for (let j = 0; j < component.v; j++) for (let k = 0; k < component.h; k++)
  311. 						decodeMcu(component, decodeFn, mcu, j, k);
  312. 				}
  313. 				mcu++;
  314. 				// If we've reached our expected MCU's, stop decoding
  315. 				if (mcu === mcuExpected) break;
  316. 			}
  317. 			// find marker
  318. 			this.bitsCount = 0;
  319. 			let marker = this.readUint16();
  320. 			if (marker < 0xFFD0 || marker > 0xFFD7) { // !RSTx
  321. 				this.seek(this.iData - 2);
  322. 				if (marker < 0xFF00) console.log('JpegImage: Error: marker was not found');
  323. 				break;
  324. 			}
  325. 		}
  326. 	}
  327. 	parse() {
  328. 		this.jfif  = null;
  329. 		this.adobe = null;
  330. 		let frame;
  331. 		let resetInterval;
  332. 		let quantizationTables = [];
  333. 		let frames             = [];
  334. 		let huffmanTablesAC    = [];
  335. 		let huffmanTablesDC    = [];
  336. 		this.seek(0);
  337. 		let fileMarker = readUint16();
  338. 		if (fileMarker != 0xFFD8) { // SOI (Start of Image)
  339. 			console.log('JpegImage: Error: SOI not found');
  340. 			return;
  341. 		}
  342. 		while ((fileMarker = readUint16()) != 0xFFD9) { // EOI (End of image)
  343. 			switch(fileMarker) {
  344. 				case 0xFF00: break;
  345. 				case 0xFFE0: // APP0 (Application Specific)
  346. 				case 0xFFE1: // APP1
  347. 				case 0xFFE2: // APP2
  348. 				case 0xFFE3: // APP3
  349. 				case 0xFFE4: // APP4
  350. 				case 0xFFE5: // APP5
  351. 				case 0xFFE6: // APP6
  352. 				case 0xFFE7: // APP7
  353. 				case 0xFFE8: // APP8
  354. 				case 0xFFE9: // APP9
  355. 				case 0xFFEA: // APP10
  356. 				case 0xFFEB: // APP11
  357. 				case 0xFFEC: // APP12
  358. 				case 0xFFED: // APP13
  359. 				case 0xFFEE: // APP14
  360. 				case 0xFFEF: // APP15
  361. 				case 0xFFFE: // COM (Comment)
  362. 					let appData = this.readDataBlock();
  363. 					switch(fileMarker){
  364. 						case 0xFFE0:
  365. 							if (
  366. 								appData[0] === 0x4A &&
  367. 								appData[1] === 0x46 &&
  368. 								appData[2] === 0x49 &&
  369. 								appData[3] === 0x46 &&
  370. 								appData[4] === 0
  371. 							) this.jfif = { // 'JFIF\x00'
  372. 								version     : { major: appData[5], minor: appData[6] },
  373. 								densityUnits: appData[7],
  374. 								xDensity    : (appData[8 ] << 8) | appData[9 ],
  375. 								yDensity    : (appData[10] << 8) | appData[11],
  376. 								thumbWidth  : appData[12],
  377. 								thumbHeight : appData[13],
  378. 								thumbData   : appData.slice(14, 14 + 3 * appData[12] * appData[13])
  379. 							};
  380. 							break;
  381. 						// TODO APP1 - Exif
  382. 						case 0xFFEE:
  383. 							if (
  384. 								appData[0] === 0x41 &&
  385. 								appData[1] === 0x64 &&
  386. 								appData[2] === 0x6F &&
  387. 								appData[3] === 0x62 &&
  388. 								appData[4] === 0x65 &&
  389. 								appData[5] === 0
  390. 							) this.adobe = { // 'Adobe\x00'
  391. 								version      : appData[6],
  392. 								flags0       : (appData[7] << 8) | appData[8],
  393. 								flags1       : (appData[9] << 8) | appData[10],
  394. 								transformCode: appData[11]
  395. 							};
  396. 							break;
  397. 					}
  398. 					break;
  399. 				case 0xFFDB: // DQT (Define Quantization Tables)
  400. 					for(let quantizationTablesLength = this.readUint16() - 2; quantizationTablesLength > 0; quantizationTablesLength--) {
  401. 						let quantizationTableSpec = this.readUint8();
  402. 						let tableData = new Int32Array(64);
  403. 						switch(quantizationTableSpec >> 4){
  404. 							case 0: // 8 bit values
  405. 									tableData.forEach((v, i) => tableData[this.dctZigZag[i]] = this.readUint8());
  406. 								break;
  407. 							case 1: //16 bit
  408. 									tableData.forEach((v, i) => tableData[this.dctZigZag[i]] = this.readUint16());
  409. 								break;
  410. 							default:
  411. 								console.log('JpegImage: Error: DQT: invalid table spec');
  412. 								return;
  413. 						}
  414. 						quantizationTables[quantizationTableSpec & 15] = tableData;
  415. 					}
  416. 					break;
  417. 				case 0xFFC0: // SOF0 (Start of Frame, Baseline DCT)
  418. 				case 0xFFC1: // SOF1 (Start of Frame, Extended DCT)
  419. 				case 0xFFC2: // SOF2 (Start of Frame, Progressive DCT)
  420. 					this.readUint16(); // skip data length
  421. 					frame = {
  422. 						extended       : fileMarker === 0xFFC1,
  423. 						progressive    : fileMarker === 0xFFC2,
  424. 						precision      : this.readUint8(),
  425. 						scanLines      : this.readUint16(),
  426. 						samplesPerLine : this.readUint16(),
  427. 						components     : {},
  428. 						componentsOrder: new Array(this.readUint8())
  429. 					};
  430. 					frame.componentsOrder.forEach((v, i) => {
  431. 						let componentId = this.readUint8();
  432. 						let b           = this.readUint8();
  433. 						frame.componentsOrder[i] = componentId;
  434. 						frame.components[componentId] = {
  435. 							h              : b >> 4,
  436. 							v              : b & 15,
  437. 							quantizationIdx: this.readUint8()
  438. 						};
  439. 					});
  440. 					this.prepareComponents(frame);
  441. 					frames.push(frame);
  442. 					break;
  443. 				case 0xFFC4: // DHT (Define Huffman Tables)
  444. 					let huffmanLength = this.readUint16() - 2;
  445. 					while (huffmanLength > 0) {
  446. 						let huffmanTableSpec = this.readUint8();
  447. 						let codeLengths      = new Uint8Array(16);
  448. 						let codeLengthSum    = 0;
  449. 						codeLengths.forEach((v, i) => codeLengthSum += (codeLengths[i] = this.readUint8()));
  450. 						let huffmanValues = new Uint8Array(codeLengthSum);
  451. 						huffmanValues.forEach((v, i) => huffmanValues[i] = this.readUint8());
  452. 						huffmanLength -= 1 + codeLengths.length + huffmanValues.length;
  453. 						((huffmanTableSpec >> 4) === 0 ? huffmanTablesDC : huffmanTablesAC)[huffmanTableSpec & 15] = this.buildHuffmanTable(codeLengths, huffmanValues);
  454. 					}
  455. 					break;
  456. 				case 0xFFDD: // DRI (Define Restart Interval)
  457. 					this.readUint16(); // skip data length
  458. 					resetInterval = this.readUint16();
  459. 					break;
  460. 				case 0xFFDA: // SOS (Start of Scan)
  461. 					this.readUint16(); // scanLength
  462. 					let components = [];
  463. 					for (let selectorsCount = this.readUint8; selectorsCount > 0; selectorsCount--) {
  464. 						let component = frame.components[this.readUint8()];
  465. 						let tableSpec = this.readUint8();
  466. 						component.huffmanTableDC = huffmanTablesDC[tableSpec >> 4];
  467. 						component.huffmanTableAC = huffmanTablesAC[tableSpec & 15];
  468. 						components.push(component);
  469. 					}
  470. 					let spectralStart = this.readUint8();
  471. 					let spectralEnd   = this.readUint8();
  472. 					let successiveApproximation = this.readUint8();
  473. 					decodeScan(
  474. 						data,
  475. 						frame,
  476. 						components,
  477. 						resetInterval,
  478. 						spectralStart,
  479. 						spectralEnd,
  480. 						successiveApproximation >> 4,
  481. 						successiveApproximation & 15
  482. 					);
  483. 					break;
  484. 				case 0xFFFF: // Fill bytes
  485. 					if (this.getUint8() !== 0xFF) this.skip(-1); // Avoid skipping a valid marker.
  486. 					break;
  487. 				default:
  488. 					this.skip(-2);
  489. 					let d1 = this.getUint8();
  490. 					this.skip(-1);
  491. 					let d0 = this.getUint(8);
  492. 					// could be incorrect encoding -- last 0xFF byte of the previous
  493. 					// block was eaten by the encoder
  494. 					if (d0 == 0xFF && d1 >= 0xC0 && d1 <= 0xFE) break;
  495. 					else {
  496. 						console.log('JpegImage: Error: unknown JPEG marker ' + fileMarker.toString(16));
  497.             			return;
  498. 					}
  499. 			}
  500. 		}
  501.  
  502.  
  503.       if (frames.length != 1)
  504.         throw new Error("only single frame JPEGs supported");
  505.  
  506.       // set each frame's components quantization table
  507.       for (var i = 0; i < frames.length; i++) {
  508.         var cp = frames[i].components;
  509.         for (var j in cp) {
  510.           cp[j].quantizationTable = quantizationTables[cp[j].quantizationIdx];
  511.           delete cp[j].quantizationIdx;
  512.         }
  513.       }
  514.  
  515.       this.width = frame.samplesPerLine;
  516.       this.height = frame.scanLines;
  517.       this.jfif = jfif;
  518.       this.adobe = adobe;
  519.       this.components = [];
  520.       for (var i = 0; i < frame.componentsOrder.length; i++) {
  521.         var component = frame.components[frame.componentsOrder[i]];
  522.         this.components.push({
  523.           lines: buildComponentData(frame, component),
  524.           scaleX: component.h / frame.maxH,
  525.           scaleY: component.v / frame.maxV
  526.         });
  527.       }
  528.  
  529.  
  530.  
  531.  
  532. 	}
  533. 	
  534.  
  535.  
  536. 	
  537. 	parse: function parse(data) {
  538.       var offset = 0, length = data.length;
  539.       function readUint16() {
  540.         var value = (data[offset] << 8) | data[offset + 1];
  541.         offset += 2;
  542.         return value;
  543.       }
  544.       function readDataBlock() {
  545.         var length = readUint16();
  546.         var array = data.subarray(offset, offset + length - 2);
  547.         offset += array.length;
  548.         return array;
  549.       }
  550.       function prepareComponents(frame) {
  551.         var maxH = 0, maxV = 0;
  552.         var component, componentId;
  553.         for (componentId in frame.components) {
  554.           if (frame.components.hasOwnProperty(componentId)) {
  555.             component = frame.components[componentId];
  556.             if (maxH < component.h) maxH = component.h;
  557.             if (maxV < component.v) maxV = component.v;
  558.           }
  559.         }
  560.         var mcusPerLine = Math.ceil(frame.samplesPerLine / 8 / maxH);
  561.         var mcusPerColumn = Math.ceil(frame.scanLines / 8 / maxV);
  562.         for (componentId in frame.components) {
  563.           if (frame.components.hasOwnProperty(componentId)) {
  564.             component = frame.components[componentId];
  565.             var blocksPerLine = Math.ceil(Math.ceil(frame.samplesPerLine / 8) * component.h / maxH);
  566.             var blocksPerColumn = Math.ceil(Math.ceil(frame.scanLines  / 8) * component.v / maxV);
  567.             var blocksPerLineForMcu = mcusPerLine * component.h;
  568.             var blocksPerColumnForMcu = mcusPerColumn * component.v;
  569.             var blocks = [];
  570.             for (var i = 0; i < blocksPerColumnForMcu; i++) {
  571.               var row = [];
  572.               for (var j = 0; j < blocksPerLineForMcu; j++)
  573.                 row.push(new Int32Array(64));
  574.               blocks.push(row);
  575.             }
  576.             component.blocksPerLine = blocksPerLine;
  577.             component.blocksPerColumn = blocksPerColumn;
  578.             component.blocks = blocks;
  579.           }
  580.         }
  581.         frame.maxH = maxH;
  582.         frame.maxV = maxV;
  583.         frame.mcusPerLine = mcusPerLine;
  584.         frame.mcusPerColumn = mcusPerColumn;
  585.       }
  586.       var jfif = null;
  587.       var adobe = null;
  588.       var pixels = null;
  589.       var frame, resetInterval;
  590.       var quantizationTables = [], frames = [];
  591.       var huffmanTablesAC = [], huffmanTablesDC = [];
  592.       var fileMarker = readUint16();
  593.       if (fileMarker != 0xFFD8) { // SOI (Start of Image)
  594.         throw new Error("SOI not found");
  595.       }
  596.  
  597.       fileMarker = readUint16();
  598.       while (fileMarker != 0xFFD9) { // EOI (End of image)
  599.         var i, j, l;
  600.         switch(fileMarker) {
  601.           case 0xFF00: break;
  602.           case 0xFFE0: // APP0 (Application Specific)
  603.           case 0xFFE1: // APP1
  604.           case 0xFFE2: // APP2
  605.           case 0xFFE3: // APP3
  606.           case 0xFFE4: // APP4
  607.           case 0xFFE5: // APP5
  608.           case 0xFFE6: // APP6
  609.           case 0xFFE7: // APP7
  610.           case 0xFFE8: // APP8
  611.           case 0xFFE9: // APP9
  612.           case 0xFFEA: // APP10
  613.           case 0xFFEB: // APP11
  614.           case 0xFFEC: // APP12
  615.           case 0xFFED: // APP13
  616.           case 0xFFEE: // APP14
  617.           case 0xFFEF: // APP15
  618.           case 0xFFFE: // COM (Comment)
  619.             var appData = readDataBlock();
  620.  
  621.             if (fileMarker === 0xFFE0) {
  622.               if (appData[0] === 0x4A && appData[1] === 0x46 && appData[2] === 0x49 &&
  623.                 appData[3] === 0x46 && appData[4] === 0) { // 'JFIF\x00'
  624.                 jfif = {
  625.                   version: { major: appData[5], minor: appData[6] },
  626.                   densityUnits: appData[7],
  627.                   xDensity: (appData[8] << 8) | appData[9],
  628.                   yDensity: (appData[10] << 8) | appData[11],
  629.                   thumbWidth: appData[12],
  630.                   thumbHeight: appData[13],
  631.                   thumbData: appData.subarray(14, 14 + 3 * appData[12] * appData[13])
  632.                 };
  633.               }
  634.             }
  635.             // TODO APP1 - Exif
  636.             if (fileMarker === 0xFFEE) {
  637.               if (appData[0] === 0x41 && appData[1] === 0x64 && appData[2] === 0x6F &&
  638.                 appData[3] === 0x62 && appData[4] === 0x65 && appData[5] === 0) { // 'Adobe\x00'
  639.                 adobe = {
  640.                   version: appData[6],
  641.                   flags0: (appData[7] << 8) | appData[8],
  642.                   flags1: (appData[9] << 8) | appData[10],
  643.                   transformCode: appData[11]
  644.                 };
  645.               }
  646.             }
  647.             break;
  648.  
  649.           case 0xFFDB: // DQT (Define Quantization Tables)
  650.             var quantizationTablesLength = readUint16();
  651.             var quantizationTablesEnd = quantizationTablesLength + offset - 2;
  652.             while (offset < quantizationTablesEnd) {
  653.               var quantizationTableSpec = data[offset++];
  654.               var tableData = new Int32Array(64);
  655.               if ((quantizationTableSpec >> 4) === 0) { // 8 bit values
  656.                 for (j = 0; j < 64; j++) {
  657.                   var z = dctZigZag[j];
  658.                   tableData[z] = data[offset++];
  659.                 }
  660.               } else if ((quantizationTableSpec >> 4) === 1) { //16 bit
  661.                 for (j = 0; j < 64; j++) {
  662.                   var z = dctZigZag[j];
  663.                   tableData[z] = readUint16();
  664.                 }
  665.               } else
  666.                 throw new Error("DQT: invalid table spec");
  667.               quantizationTables[quantizationTableSpec & 15] = tableData;
  668.             }
  669.             break;
  670.  
  671.           case 0xFFC0: // SOF0 (Start of Frame, Baseline DCT)
  672.           case 0xFFC1: // SOF1 (Start of Frame, Extended DCT)
  673.           case 0xFFC2: // SOF2 (Start of Frame, Progressive DCT)
  674.             readUint16(); // skip data length
  675.             frame = {};
  676.             frame.extended = (fileMarker === 0xFFC1);
  677.             frame.progressive = (fileMarker === 0xFFC2);
  678.             frame.precision = data[offset++];
  679.             frame.scanLines = readUint16();
  680.             frame.samplesPerLine = readUint16();
  681.             frame.components = {};
  682.             frame.componentsOrder = [];
  683.             var componentsCount = data[offset++], componentId;
  684.             var maxH = 0, maxV = 0;
  685.             for (i = 0; i < componentsCount; i++) {
  686.               componentId = data[offset];
  687.               var h = data[offset + 1] >> 4;
  688.               var v = data[offset + 1] & 15;
  689.               var qId = data[offset + 2];
  690.               frame.componentsOrder.push(componentId);
  691.               frame.components[componentId] = {
  692.                 h: h,
  693.                 v: v,
  694.                 quantizationIdx: qId
  695.               };
  696.               offset += 3;
  697.             }
  698.             prepareComponents(frame);
  699.             frames.push(frame);
  700.             break;
  701.  
  702.           case 0xFFC4: // DHT (Define Huffman Tables)
  703.             var huffmanLength = readUint16();
  704.             for (i = 2; i < huffmanLength;) {
  705.               var huffmanTableSpec = data[offset++];
  706.               var codeLengths = new Uint8Array(16);
  707.               var codeLengthSum = 0;
  708.               for (j = 0; j < 16; j++, offset++)
  709.                 codeLengthSum += (codeLengths[j] = data[offset]);
  710.               var huffmanValues = new Uint8Array(codeLengthSum);
  711.               for (j = 0; j < codeLengthSum; j++, offset++)
  712.                 huffmanValues[j] = data[offset];
  713.               i += 17 + codeLengthSum;
  714.  
  715.               ((huffmanTableSpec >> 4) === 0 ?
  716.                 huffmanTablesDC : huffmanTablesAC)[huffmanTableSpec & 15] =
  717.                 buildHuffmanTable(codeLengths, huffmanValues);
  718.             }
  719.             break;
  720.  
  721.           case 0xFFDD: // DRI (Define Restart Interval)
  722.             readUint16(); // skip data length
  723.             resetInterval = readUint16();
  724.             break;
  725.  
  726.           case 0xFFDA: // SOS (Start of Scan)
  727.             var scanLength = readUint16();
  728.             var selectorsCount = data[offset++];
  729.             var components = [], component;
  730.             for (i = 0; i < selectorsCount; i++) {
  731.               component = frame.components[data[offset++]];
  732.               var tableSpec = data[offset++];
  733.               component.huffmanTableDC = huffmanTablesDC[tableSpec >> 4];
  734.               component.huffmanTableAC = huffmanTablesAC[tableSpec & 15];
  735.               components.push(component);
  736.             }
  737.             var spectralStart = data[offset++];
  738.             var spectralEnd = data[offset++];
  739.             var successiveApproximation = data[offset++];
  740.             var processed = decodeScan(data, offset,
  741.               frame, components, resetInterval,
  742.               spectralStart, spectralEnd,
  743.               successiveApproximation >> 4, successiveApproximation & 15);
  744.             offset += processed;
  745.             break;
  746.  
  747.           case 0xFFFF: // Fill bytes
  748.             if (data[offset] !== 0xFF) { // Avoid skipping a valid marker.
  749.               offset--;
  750.             }
  751.             break;
  752.  
  753.           default:
  754.             if (data[offset - 3] == 0xFF &&
  755.                 data[offset - 2] >= 0xC0 && data[offset - 2] <= 0xFE) {
  756.               // could be incorrect encoding -- last 0xFF byte of the previous
  757.               // block was eaten by the encoder
  758.               offset -= 3;
  759.               break;
  760.             }
  761.             throw new Error("unknown JPEG marker " + fileMarker.toString(16));
  762.         }
  763.         fileMarker = readUint16();
  764.       }
  765.       if (frames.length != 1)
  766.         throw new Error("only single frame JPEGs supported");
  767.  
  768.       // set each frame's components quantization table
  769.       for (var i = 0; i < frames.length; i++) {
  770.         var cp = frames[i].components;
  771.         for (var j in cp) {
  772.           cp[j].quantizationTable = quantizationTables[cp[j].quantizationIdx];
  773.           delete cp[j].quantizationIdx;
  774.         }
  775.       }
  776.  
  777.       this.width = frame.samplesPerLine;
  778.       this.height = frame.scanLines;
  779.       this.jfif = jfif;
  780.       this.adobe = adobe;
  781.       this.components = [];
  782.       for (var i = 0; i < frame.componentsOrder.length; i++) {
  783.         var component = frame.components[frame.componentsOrder[i]];
  784.         this.components.push({
  785.           lines: buildComponentData(frame, component),
  786.           scaleX: component.h / frame.maxH,
  787.           scaleY: component.v / frame.maxV
  788.         });
  789.       }
  790.     },
  791.  
  792. 	
  793. 	
  794. 	
  795. }
  796.  
  797. class Jpeg {
  798. 	decode(jpegData) {
  799. 		
  800. 	}
  801. }
  802.  
  803. jpeg = new Jpeg();