118 lines
2.4 KiB
JavaScript
118 lines
2.4 KiB
JavaScript
'use strict';
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var ParserStream = require('../common').ParserStream;
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// part of parseJpegMarker called after skipping initial FF
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function parseJpegMarker_afterFF(parser, callback) {
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parser._bytes(1, function (data) {
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var code = data[0];
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if (code === 0xFF) {
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// padding byte, skip it
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parseJpegMarker_afterFF(parser, callback);
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return;
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}
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// standalone markers, according to JPEG 1992,
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// http://www.w3.org/Graphics/JPEG/itu-t81.pdf, see Table B.1
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if ((0xD0 <= code && code <= 0xD9) || code === 0x01) {
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callback(code, 0);
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return;
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}
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// the rest of the unreserved markers
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if (0xC0 <= code && code <= 0xFE) {
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parser._bytes(2, function (length) {
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callback(code, length.readUInt16BE(0) - 2);
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});
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return;
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}
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// unknown markers
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callback();
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});
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}
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function parseJpegMarker(parser, callback) {
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parser._bytes(1, function (data) {
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if (data[0] !== 0xFF) {
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// not a JPEG marker
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callback();
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return;
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}
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parseJpegMarker_afterFF(parser, callback);
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});
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}
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function getJpegSize(parser) {
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parseJpegMarker(parser, function (code, length) {
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if (!code || length < 0) {
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// invalid jpeg
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parser._skipBytes(Infinity);
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parser.push(null);
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return;
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}
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if (code === 0xD9 /* EOI */ || code === 0xDA /* SOS */) {
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// end of the datastream
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parser._skipBytes(Infinity);
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parser.push(null);
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return;
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}
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if (length <= 0) {
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// e.g. empty comment
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getJpegSize(parser);
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return;
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}
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if (length >= 5 &&
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(0xC0 <= code && code <= 0xCF) &&
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code !== 0xC4 && code !== 0xC8 && code !== 0xCC) {
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parser._bytes(length, function (data) {
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parser._skipBytes(Infinity);
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parser.push({
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width: data.readUInt16BE(3),
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height: data.readUInt16BE(1),
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type: 'jpg',
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mime: 'image/jpeg',
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wUnits: 'px',
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hUnits: 'px'
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});
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parser.push(null);
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});
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return;
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}
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parser._skipBytes(length, function () {
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getJpegSize(parser);
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});
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});
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}
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module.exports = function () {
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var parser = new ParserStream();
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parser._bytes(2, function (data) {
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if (data[0] !== 0xFF || data[1] !== 0xD8) {
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// first marker of the file MUST be 0xFFD8
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parser._skipBytes(Infinity);
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parser.push(null);
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return;
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}
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getJpegSize(parser);
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});
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return parser;
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};
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