gzh_chuanyuan/uni_modules/lime-shared/exif/index.ts

// @ts-nocheck
import { base64ToArrayBuffer } from '../base64ToArrayBuffer';
import { pathToBase64 } from '../pathToBase64';
import { isBase64 } from '../isBase64';
import { isString } from '../isString';

interface File {
	exifdata : any
	iptcdata : any
	xmpdata : any
	src : string
}
class EXIF {
	isXmpEnabled = false
	debug = false
	Tags = {
		// version tags
		0x9000: "ExifVersion", // EXIF version
		0xA000: "FlashpixVersion", // Flashpix format version

		// colorspace tags
		0xA001: "ColorSpace", // Color space information tag

		// image configuration
		0xA002: "PixelXDimension", // Valid width of meaningful image
		0xA003: "PixelYDimension", // Valid height of meaningful image
		0x9101: "ComponentsConfiguration", // Information about channels
		0x9102: "CompressedBitsPerPixel", // Compressed bits per pixel

		// user information
		0x927C: "MakerNote", // Any desired information written by the manufacturer
		0x9286: "UserComment", // Comments by user

		// related file
		0xA004: "RelatedSoundFile", // Name of related sound file

		// date and time
		0x9003: "DateTimeOriginal", // Date and time when the original image was generated
		0x9004: "DateTimeDigitized", // Date and time when the image was stored digitally
		0x9290: "SubsecTime", // Fractions of seconds for DateTime
		0x9291: "SubsecTimeOriginal", // Fractions of seconds for DateTimeOriginal
		0x9292: "SubsecTimeDigitized", // Fractions of seconds for DateTimeDigitized

		// picture-taking conditions
		0x829A: "ExposureTime", // Exposure time (in seconds)
		0x829D: "FNumber", // F number
		0x8822: "ExposureProgram", // Exposure program
		0x8824: "SpectralSensitivity", // Spectral sensitivity
		0x8827: "ISOSpeedRatings", // ISO speed rating
		0x8828: "OECF", // Optoelectric conversion factor
		0x9201: "ShutterSpeedValue", // Shutter speed
		0x9202: "ApertureValue", // Lens aperture
		0x9203: "BrightnessValue", // Value of brightness
		0x9204: "ExposureBias", // Exposure bias
		0x9205: "MaxApertureValue", // Smallest F number of lens
		0x9206: "SubjectDistance", // Distance to subject in meters
		0x9207: "MeteringMode", // Metering mode
		0x9208: "LightSource", // Kind of light source
		0x9209: "Flash", // Flash status
		0x9214: "SubjectArea", // Location and area of main subject
		0x920A: "FocalLength", // Focal length of the lens in mm
		0xA20B: "FlashEnergy", // Strobe energy in BCPS
		0xA20C: "SpatialFrequencyResponse", //
		0xA20E: "FocalPlaneXResolution", // Number of pixels in width direction per FocalPlaneResolutionUnit
		0xA20F: "FocalPlaneYResolution", // Number of pixels in height direction per FocalPlaneResolutionUnit
		0xA210: "FocalPlaneResolutionUnit", // Unit for measuring FocalPlaneXResolution and FocalPlaneYResolution
		0xA214: "SubjectLocation", // Location of subject in image
		0xA215: "ExposureIndex", // Exposure index selected on camera
		0xA217: "SensingMethod", // Image sensor type
		0xA300: "FileSource", // Image source (3 == DSC)
		0xA301: "SceneType", // Scene type (1 == directly photographed)
		0xA302: "CFAPattern", // Color filter array geometric pattern
		0xA401: "CustomRendered", // Special processing
		0xA402: "ExposureMode", // Exposure mode
		0xA403: "WhiteBalance", // 1 = auto white balance, 2 = manual
		0xA404: "DigitalZoomRation", // Digital zoom ratio
		0xA405: "FocalLengthIn35mmFilm", // Equivalent foacl length assuming 35mm film camera (in mm)
		0xA406: "SceneCaptureType", // Type of scene
		0xA407: "GainControl", // Degree of overall image gain adjustment
		0xA408: "Contrast", // Direction of contrast processing applied by camera
		0xA409: "Saturation", // Direction of saturation processing applied by camera
		0xA40A: "Sharpness", // Direction of sharpness processing applied by camera
		0xA40B: "DeviceSettingDescription", //
		0xA40C: "SubjectDistanceRange", // Distance to subject

		// other tags
		0xA005: "InteroperabilityIFDPointer",
		0xA420: "ImageUniqueID" // Identifier assigned uniquely to each image
	}
	TiffTags = {
		0x0100: "ImageWidth",
		0x0101: "ImageHeight",
		0x8769: "ExifIFDPointer",
		0x8825: "GPSInfoIFDPointer",
		0xA005: "InteroperabilityIFDPointer",
		0x0102: "BitsPerSample",
		0x0103: "Compression",
		0x0106: "PhotometricInterpretation",
		0x0112: "Orientation",
		0x0115: "SamplesPerPixel",
		0x011C: "PlanarConfiguration",
		0x0212: "YCbCrSubSampling",
		0x0213: "YCbCrPositioning",
		0x011A: "XResolution",
		0x011B: "YResolution",
		0x0128: "ResolutionUnit",
		0x0111: "StripOffsets",
		0x0116: "RowsPerStrip",
		0x0117: "StripByteCounts",
		0x0201: "JPEGInterchangeFormat",
		0x0202: "JPEGInterchangeFormatLength",
		0x012D: "TransferFunction",
		0x013E: "WhitePoint",
		0x013F: "PrimaryChromaticities",
		0x0211: "YCbCrCoefficients",
		0x0214: "ReferenceBlackWhite",
		0x0132: "DateTime",
		0x010E: "ImageDescription",
		0x010F: "Make",
		0x0110: "Model",
		0x0131: "Software",
		0x013B: "Artist",
		0x8298: "Copyright"
	}
	GPSTags = {
		0x0000: "GPSVersionID",
		0x0001: "GPSLatitudeRef",
		0x0002: "GPSLatitude",
		0x0003: "GPSLongitudeRef",
		0x0004: "GPSLongitude",
		0x0005: "GPSAltitudeRef",
		0x0006: "GPSAltitude",
		0x0007: "GPSTimeStamp",
		0x0008: "GPSSatellites",
		0x0009: "GPSStatus",
		0x000A: "GPSMeasureMode",
		0x000B: "GPSDOP",
		0x000C: "GPSSpeedRef",
		0x000D: "GPSSpeed",
		0x000E: "GPSTrackRef",
		0x000F: "GPSTrack",
		0x0010: "GPSImgDirectionRef",
		0x0011: "GPSImgDirection",
		0x0012: "GPSMapDatum",
		0x0013: "GPSDestLatitudeRef",
		0x0014: "GPSDestLatitude",
		0x0015: "GPSDestLongitudeRef",
		0x0016: "GPSDestLongitude",
		0x0017: "GPSDestBearingRef",
		0x0018: "GPSDestBearing",
		0x0019: "GPSDestDistanceRef",
		0x001A: "GPSDestDistance",
		0x001B: "GPSProcessingMethod",
		0x001C: "GPSAreaInformation",
		0x001D: "GPSDateStamp",
		0x001E: "GPSDifferential"
	}
	// EXIF 2.3 Spec
	IFD1Tags = {
		0x0100: "ImageWidth",
		0x0101: "ImageHeight",
		0x0102: "BitsPerSample",
		0x0103: "Compression",
		0x0106: "PhotometricInterpretation",
		0x0111: "StripOffsets",
		0x0112: "Orientation",
		0x0115: "SamplesPerPixel",
		0x0116: "RowsPerStrip",
		0x0117: "StripByteCounts",
		0x011A: "XResolution",
		0x011B: "YResolution",
		0x011C: "PlanarConfiguration",
		0x0128: "ResolutionUnit",
		0x0201: "JpegIFOffset", // When image format is JPEG, this value show offset to JPEG data stored.(aka "ThumbnailOffset" or "JPEGInterchangeFormat")
		0x0202: "JpegIFByteCount", // When image format is JPEG, this value shows data size of JPEG image (aka "ThumbnailLength" or "JPEGInterchangeFormatLength")
		0x0211: "YCbCrCoefficients",
		0x0212: "YCbCrSubSampling",
		0x0213: "YCbCrPositioning",
		0x0214: "ReferenceBlackWhite"
	}
	StringValues = {
		ExposureProgram: {
			0: "Not defined",
			1: "Manual",
			2: "Normal program",
			3: "Aperture priority",
			4: "Shutter priority",
			5: "Creative program",
			6: "Action program",
			7: "Portrait mode",
			8: "Landscape mode"
		},
		MeteringMode: {
			0: "Unknown",
			1: "Average",
			2: "CenterWeightedAverage",
			3: "Spot",
			4: "MultiSpot",
			5: "Pattern",
			6: "Partial",
			255: "Other"
		},
		LightSource: {
			0: "Unknown",
			1: "Daylight",
			2: "Fluorescent",
			3: "Tungsten (incandescent light)",
			4: "Flash",
			9: "Fine weather",
			10: "Cloudy weather",
			11: "Shade",
			12: "Daylight fluorescent (D 5700 - 7100K)",
			13: "Day white fluorescent (N 4600 - 5400K)",
			14: "Cool white fluorescent (W 3900 - 4500K)",
			15: "White fluorescent (WW 3200 - 3700K)",
			17: "Standard light A",
			18: "Standard light B",
			19: "Standard light C",
			20: "D55",
			21: "D65",
			22: "D75",
			23: "D50",
			24: "ISO studio tungsten",
			255: "Other"
		},
		Flash: {
			0x0000: "Flash did not fire",
			0x0001: "Flash fired",
			0x0005: "Strobe return light not detected",
			0x0007: "Strobe return light detected",
			0x0009: "Flash fired, compulsory flash mode",
			0x000D: "Flash fired, compulsory flash mode, return light not detected",
			0x000F: "Flash fired, compulsory flash mode, return light detected",
			0x0010: "Flash did not fire, compulsory flash mode",
			0x0018: "Flash did not fire, auto mode",
			0x0019: "Flash fired, auto mode",
			0x001D: "Flash fired, auto mode, return light not detected",
			0x001F: "Flash fired, auto mode, return light detected",
			0x0020: "No flash function",
			0x0041: "Flash fired, red-eye reduction mode",
			0x0045: "Flash fired, red-eye reduction mode, return light not detected",
			0x0047: "Flash fired, red-eye reduction mode, return light detected",
			0x0049: "Flash fired, compulsory flash mode, red-eye reduction mode",
			0x004D: "Flash fired, compulsory flash mode, red-eye reduction mode, return light not detected",
			0x004F: "Flash fired, compulsory flash mode, red-eye reduction mode, return light detected",
			0x0059: "Flash fired, auto mode, red-eye reduction mode",
			0x005D: "Flash fired, auto mode, return light not detected, red-eye reduction mode",
			0x005F: "Flash fired, auto mode, return light detected, red-eye reduction mode"
		},
		SensingMethod: {
			1: "Not defined",
			2: "One-chip color area sensor",
			3: "Two-chip color area sensor",
			4: "Three-chip color area sensor",
			5: "Color sequential area sensor",
			7: "Trilinear sensor",
			8: "Color sequential linear sensor"
		},
		SceneCaptureType: {
			0: "Standard",
			1: "Landscape",
			2: "Portrait",
			3: "Night scene"
		},
		SceneType: {
			1: "Directly photographed"
		},
		CustomRendered: {
			0: "Normal process",
			1: "Custom process"
		},
		WhiteBalance: {
			0: "Auto white balance",
			1: "Manual white balance"
		},
		GainControl: {
			0: "None",
			1: "Low gain up",
			2: "High gain up",
			3: "Low gain down",
			4: "High gain down"
		},
		Contrast: {
			0: "Normal",
			1: "Soft",
			2: "Hard"
		},
		Saturation: {
			0: "Normal",
			1: "Low saturation",
			2: "High saturation"
		},
		Sharpness: {
			0: "Normal",
			1: "Soft",
			2: "Hard"
		},
		SubjectDistanceRange: {
			0: "Unknown",
			1: "Macro",
			2: "Close view",
			3: "Distant view"
		},
		FileSource: {
			3: "DSC"
		},

		Components: {
			0: "",
			1: "Y",
			2: "Cb",
			3: "Cr",
			4: "R",
			5: "G",
			6: "B"
		}
	}
	enableXmp() {
		this.isXmpEnabled = true
	}
	disableXmp() {
		this.isXmpEnabled = false;
	}
	/**
	 * 获取图片数据
	 * @param img 图片地址
	 * @param callback 回调 返回图片数据
	 * */
	getData(img : any, callback : Function) {
		// if (((self.Image && img instanceof self.Image) || (self.HTMLImageElement && img instanceof self.HTMLImageElement)) && !img.complete)
		// 	return false;
		let file : File = {
			src: '',
			exifdata: null,
			iptcdata: null,
			xmpdata: null,
		}
		if (isBase64(img)) {
			file.src = img
		} else if (img.path) {
			file.src = img.path
		} else if (isString(img)) {
			file.src = img
		} else {
			return false;
		}


		if (!imageHasData(file)) {
			getImageData(file, callback);
		} else {
			if (callback) {
				callback.call(file);
			}
		}
		return true;
	}
	/**
	 * 获取图片tag
	 * @param img 图片数据
	 * @param tag tag 类型
	 * */
	getTag(img : File, tag : string) {
		if (!imageHasData(img)) return;
		return img.exifdata[tag];
	}
	getIptcTag(img : File, tag : string) {
		if (!imageHasData(img)) return;
		return img.iptcdata[tag];
	}
	getAllTags(img : File) {
		if (!imageHasData(img)) return {};
		let a,
			data = img.exifdata,
			tags = {};
		for (a in data) {
			if (data.hasOwnProperty(a)) {
				tags[a] = data[a];
			}
		}
		return tags;
	}
	getAllIptcTags(img : File) {
		if (!imageHasData(img)) return {};
		let a,
			data = img.iptcdata,
			tags = {};
		for (a in data) {
			if (data.hasOwnProperty(a)) {
				tags[a] = data[a];
			}
		}
		return tags;
	}
	pretty(img : File) {
		if (!imageHasData(img)) return "";
		let a,
			data = img.exifdata,
			strPretty = "";
		for (a in data) {
			if (data.hasOwnProperty(a)) {
				if (typeof data[a] == "object") {
					if (data[a] instanceof Number) {
						strPretty += a + " : " + data[a] + " [" + data[a].numerator + "/" + data[a]
							.denominator + "]\r\n";
					} else {
						strPretty += a + " : [" + data[a].length + " values]\r\n";
					}
				} else {
					strPretty += a + " : " + data[a] + "\r\n";
				}
			}
		}
		return strPretty;
	}
	readFromBinaryFile(file: ArrayBuffer) {
		return findEXIFinJPEG(file);
	}
}

export const exif = new EXIF()
// export function getData(img, callback) {
// 	const exif = new EXIF()
// 	exif.getData(img, callback)
// }

// export default {getData}
const ExifTags = exif.Tags
const TiffTags = exif.TiffTags
const IFD1Tags = exif.IFD1Tags
const GPSTags = exif.GPSTags
const StringValues = exif.StringValues


function imageHasData(img : File) : boolean {
	return !!(img.exifdata);
}

function objectURLToBlob(url : string, callback : Function) {
	try {
		const http = new XMLHttpRequest();
		http.open("GET", url, true);
		http.responseType = "blob";
		http.onload = function (e) {
			if (this.status == 200 || this.status === 0) {
				callback(this.response);
			}
		};
		http.send();
	} catch (e) {
		console.warn(e)
	}
}


function getImageData(img : File, callback : Function) {
	function handleBinaryFile(binFile: ArrayBuffer) {
		const data = findEXIFinJPEG(binFile);
		img.exifdata = data ?? {};
		const iptcdata = findIPTCinJPEG(binFile);
		img.iptcdata = iptcdata ?? {};
		if (exif.isXmpEnabled) {
			const xmpdata = findXMPinJPEG(binFile);
			img.xmpdata = xmpdata ?? {};
		}
		if (callback) {
			callback.call(img);
		}
	}

	if (img.src) {
		if (/^data\:/i.test(img.src)) { // Data URI
			// var arrayBuffer = base64ToArrayBuffer(img.src);
			handleBinaryFile(base64ToArrayBuffer(img.src));

		} else if (/^blob\:/i.test(img.src) && typeof FileReader !== 'undefined') { // Object URL
			var fileReader = new FileReader();
			fileReader.onload = function (e) {
				handleBinaryFile(e.target.result);
			};
			objectURLToBlob(img.src, function (blob : Blob) {
				fileReader.readAsArrayBuffer(blob);
			});
		} else if (typeof XMLHttpRequest !== 'undefined') {
			var http = new XMLHttpRequest();
			http.onload = function () {
				if (this.status == 200 || this.status === 0) {
					handleBinaryFile(http.response);
				} else {
					throw "Could not load image";
				}
				http = null;
			};
			http.open("GET", img.src, true);
			http.responseType = "arraybuffer";
			http.send(null);
		} else {
			pathToBase64(img.src).then(res => {
				handleBinaryFile(base64ToArrayBuffer(res));
			})
		}
	} else if (typeof FileReader !== 'undefined' && self.FileReader && (img instanceof self.Blob || img instanceof self.File)) {
		var fileReader = new FileReader();
		fileReader.onload = function (e : any) {
			if (exif.debug) console.log("Got file of length " + e.target.result.byteLength);
			handleBinaryFile(e.target.result);
		};

		fileReader.readAsArrayBuffer(img);
	}
}

function findEXIFinJPEG(file: ArrayBuffer) {
	const dataView = new DataView(file);

	if (exif.debug) console.log("Got file of length " + file.byteLength);
	if ((dataView.getUint8(0) != 0xFF) || (dataView.getUint8(1) != 0xD8)) {
		if (exif.debug) console.log("Not a valid JPEG");
		return false; // not a valid jpeg
	}

	let offset = 2,
		length = file.byteLength,
		marker;

	while (offset < length) {
		if (dataView.getUint8(offset) != 0xFF) {
			if (exif.debug) console.log("Not a valid marker at offset " + offset + ", found: " + dataView.getUint8(
				offset));
			return false; // not a valid marker, something is wrong
		}

		marker = dataView.getUint8(offset + 1);
		if (exif.debug) console.log(marker);

		// we could implement handling for other markers here,
		// but we're only looking for 0xFFE1 for EXIF data

		if (marker == 225) {
			if (exif.debug) console.log("Found 0xFFE1 marker");

			return readEXIFData(dataView, offset + 4, dataView.getUint16(offset + 2) - 2);

			// offset += 2 + file.getShortAt(offset+2, true);

		} else {
			offset += 2 + dataView.getUint16(offset + 2);
		}

	}

}

function findIPTCinJPEG(file: ArrayBuffer) {
	const dataView = new DataView(file);

	if (exif.debug) console.log("Got file of length " + file.byteLength);
	if ((dataView.getUint8(0) != 0xFF) || (dataView.getUint8(1) != 0xD8)) {
		if (exif.debug) console.log("Not a valid JPEG");
		return false; // not a valid jpeg
	}

	let offset = 2,
		length = file.byteLength;


	const isFieldSegmentStart = function (dataView, offset: number) {
		return (
			dataView.getUint8(offset) === 0x38 &&
			dataView.getUint8(offset + 1) === 0x42 &&
			dataView.getUint8(offset + 2) === 0x49 &&
			dataView.getUint8(offset + 3) === 0x4D &&
			dataView.getUint8(offset + 4) === 0x04 &&
			dataView.getUint8(offset + 5) === 0x04
		);
	};

	while (offset < length) {

		if (isFieldSegmentStart(dataView, offset)) {

			// Get the length of the name header (which is padded to an even number of bytes)
			var nameHeaderLength = dataView.getUint8(offset + 7);
			if (nameHeaderLength % 2 !== 0) nameHeaderLength += 1;
			// Check for pre photoshop 6 format
			if (nameHeaderLength === 0) {
				// Always 4
				nameHeaderLength = 4;
			}

			var startOffset = offset + 8 + nameHeaderLength;
			var sectionLength = dataView.getUint16(offset + 6 + nameHeaderLength);

			return readIPTCData(file, startOffset, sectionLength);

			break;

		}


		// Not the marker, continue searching
		offset++;

	}

}

const IptcFieldMap = {
	0x78: 'caption',
	0x6E: 'credit',
	0x19: 'keywords',
	0x37: 'dateCreated',
	0x50: 'byline',
	0x55: 'bylineTitle',
	0x7A: 'captionWriter',
	0x69: 'headline',
	0x74: 'copyright',
	0x0F: 'category'
};

function readIPTCData(file: ArrayBuffer, startOffset: number, sectionLength: number) {
	const dataView = new DataView(file);
	let data = {};
	let fieldValue, fieldName, dataSize, segmentType, segmentSize;
	let segmentStartPos = startOffset;
	while (segmentStartPos < startOffset + sectionLength) {
		if (dataView.getUint8(segmentStartPos) === 0x1C && dataView.getUint8(segmentStartPos + 1) === 0x02) {
			segmentType = dataView.getUint8(segmentStartPos + 2);
			if (segmentType in IptcFieldMap) {
				dataSize = dataView.getInt16(segmentStartPos + 3);
				segmentSize = dataSize + 5;
				fieldName = IptcFieldMap[segmentType];
				fieldValue = getStringFromDB(dataView, segmentStartPos + 5, dataSize);
				// Check if we already stored a value with this name
				if (data.hasOwnProperty(fieldName)) {
					// Value already stored with this name, create multivalue field
					if (data[fieldName] instanceof Array) {
						data[fieldName].push(fieldValue);
					} else {
						data[fieldName] = [data[fieldName], fieldValue];
					}
				} else {
					data[fieldName] = fieldValue;
				}
			}

		}
		segmentStartPos++;
	}
	return data;
}

function readTags(file: DataView, tiffStart: number, dirStart: number, strings: any[], bigEnd: number) {
	let entries = file.getUint16(dirStart, !bigEnd),
		tags = {},
		entryOffset, tag;

	for (let i = 0; i < entries; i++) {
		entryOffset = dirStart + i * 12 + 2;
		tag = strings[file.getUint16(entryOffset, !bigEnd)];
		if (!tag && exif.debug) console.log("Unknown tag: " + file.getUint16(entryOffset, !bigEnd));
		tags[tag] = readTagValue(file, entryOffset, tiffStart, dirStart, bigEnd);
	}
	return tags;
}

function readTagValue(file: DataView, entryOffset: number, tiffStart: number, dirStart: number, bigEnd: number) {
	let type = file.getUint16(entryOffset + 2, !bigEnd),
		numValues = file.getUint32(entryOffset + 4, !bigEnd),
		valueOffset = file.getUint32(entryOffset + 8, !bigEnd) + tiffStart,
		offset,
		vals, val, n,
		numerator, denominator;

	switch (type) {
		case 1: // byte, 8-bit unsigned int
		case 7: // undefined, 8-bit byte, value depending on field
			if (numValues == 1) {
				return file.getUint8(entryOffset + 8, !bigEnd);
			} else {
				offset = numValues > 4 ? valueOffset : (entryOffset + 8);
				vals = [];
				for (n = 0; n < numValues; n++) {
					vals[n] = file.getUint8(offset + n);
				}
				return vals;
			}

		case 2: // ascii, 8-bit byte
			offset = numValues > 4 ? valueOffset : (entryOffset + 8);
			return getStringFromDB(file, offset, numValues - 1);

		case 3: // short, 16 bit int
			if (numValues == 1) {
				return file.getUint16(entryOffset + 8, !bigEnd);
			} else {
				offset = numValues > 2 ? valueOffset : (entryOffset + 8);
				vals = [];
				for (n = 0; n < numValues; n++) {
					vals[n] = file.getUint16(offset + 2 * n, !bigEnd);
				}
				return vals;
			}

		case 4: // long, 32 bit int
			if (numValues == 1) {
				return file.getUint32(entryOffset + 8, !bigEnd);
			} else {
				vals = [];
				for (n = 0; n < numValues; n++) {
					vals[n] = file.getUint32(valueOffset + 4 * n, !bigEnd);
				}
				return vals;
			}

		case 5: // rational = two long values, first is numerator, second is denominator
			if (numValues == 1) {
				numerator = file.getUint32(valueOffset, !bigEnd);
				denominator = file.getUint32(valueOffset + 4, !bigEnd);
				val = new Number(numerator / denominator);
				val.numerator = numerator;
				val.denominator = denominator;
				return val;
			} else {
				vals = [];
				for (n = 0; n < numValues; n++) {
					numerator = file.getUint32(valueOffset + 8 * n, !bigEnd);
					denominator = file.getUint32(valueOffset + 4 + 8 * n, !bigEnd);
					vals[n] = new Number(numerator / denominator);
					vals[n].numerator = numerator;
					vals[n].denominator = denominator;
				}
				return vals;
			}

		case 9: // slong, 32 bit signed int
			if (numValues == 1) {
				return file.getInt32(entryOffset + 8, !bigEnd);
			} else {
				vals = [];
				for (n = 0; n < numValues; n++) {
					vals[n] = file.getInt32(valueOffset + 4 * n, !bigEnd);
				}
				return vals;
			}

		case 10: // signed rational, two slongs, first is numerator, second is denominator
			if (numValues == 1) {
				return file.getInt32(valueOffset, !bigEnd) / file.getInt32(valueOffset + 4, !bigEnd);
			} else {
				vals = [];
				for (n = 0; n < numValues; n++) {
					vals[n] = file.getInt32(valueOffset + 8 * n, !bigEnd) / file.getInt32(valueOffset + 4 + 8 *
						n, !bigEnd);
				}
				return vals;
			}
	}
}
/**
	 * Given an IFD (Image File Directory) start offset
	 * returns an offset to next IFD or 0 if it's the last IFD.
	 */
function getNextIFDOffset(dataView: DataView, dirStart: number, bigEnd: number) {
	//the first 2bytes means the number of directory entries contains in this IFD
	var entries = dataView.getUint16(dirStart, !bigEnd);

	// After last directory entry, there is a 4bytes of data,
	// it means an offset to next IFD.
	// If its value is '0x00000000', it means this is the last IFD and there is no linked IFD.

	return dataView.getUint32(dirStart + 2 + entries * 12, !bigEnd); // each entry is 12 bytes long
}

function readThumbnailImage(dataView: DataView, tiffStart: number, firstIFDOffset: number, bigEnd: number) {
	// get the IFD1 offset
	const IFD1OffsetPointer = getNextIFDOffset(dataView, tiffStart + firstIFDOffset, bigEnd);

	if (!IFD1OffsetPointer) {
		// console.log('******** IFD1Offset is empty, image thumb not found ********');
		return {};
	} else if (IFD1OffsetPointer > dataView.byteLength) { // this should not happen
		// console.log('******** IFD1Offset is outside the bounds of the DataView ********');
		return {};
	}
	// console.log('*******  thumbnail IFD offset (IFD1) is: %s', IFD1OffsetPointer);

	let thumbTags : any = readTags(dataView, tiffStart, tiffStart + IFD1OffsetPointer, IFD1Tags, bigEnd)

	// EXIF 2.3 specification for JPEG format thumbnail

	// If the value of Compression(0x0103) Tag in IFD1 is '6', thumbnail image format is JPEG.
	// Most of Exif image uses JPEG format for thumbnail. In that case, you can get offset of thumbnail
	// by JpegIFOffset(0x0201) Tag in IFD1, size of thumbnail by JpegIFByteCount(0x0202) Tag.
	// Data format is ordinary JPEG format, starts from 0xFFD8 and ends by 0xFFD9. It seems that
	// JPEG format and 160x120pixels of size are recommended thumbnail format for Exif2.1 or later.

	if (thumbTags['Compression'] && typeof Blob !== 'undefined') {
		// console.log('Thumbnail image found!');

		switch (thumbTags['Compression']) {
			case 6:
				// console.log('Thumbnail image format is JPEG');
				if (thumbTags.JpegIFOffset && thumbTags.JpegIFByteCount) {
					// extract the thumbnail
					var tOffset = tiffStart + thumbTags.JpegIFOffset;
					var tLength = thumbTags.JpegIFByteCount;
					thumbTags['blob'] = new Blob([new Uint8Array(dataView.buffer, tOffset, tLength)], {
						type: 'image/jpeg'
					});
				}
				break;

			case 1:
				console.log("Thumbnail image format is TIFF, which is not implemented.");
				break;
			default:
				console.log("Unknown thumbnail image format '%s'", thumbTags['Compression']);
		}
	} else if (thumbTags['PhotometricInterpretation'] == 2) {
		console.log("Thumbnail image format is RGB, which is not implemented.");
	}
	return thumbTags;
}

function getStringFromDB(buffer: DataView, start: number, length: number) {
	let outstr = "";
	for (let n = start; n < start + length; n++) {
		outstr += String.fromCharCode(buffer.getUint8(n));
	}
	return outstr;
}

function readEXIFData(file: DataView, start: number) {
	if (getStringFromDB(file, start, 4) != "Exif") {
		if (exif.debug) console.log("Not valid EXIF data! " + getStringFromDB(file, start, 4));
		return false;
	}

	let bigEnd,
		tags, tag,
		exifData, gpsData,
		tiffOffset = start + 6;

	// test for TIFF validity and endianness
	if (file.getUint16(tiffOffset) == 0x4949) {
		bigEnd = false;
	} else if (file.getUint16(tiffOffset) == 0x4D4D) {
		bigEnd = true;
	} else {
		if (exif.debug) console.log("Not valid TIFF data! (no 0x4949 or 0x4D4D)");
		return false;
	}

	if (file.getUint16(tiffOffset + 2, !bigEnd) != 0x002A) {
		if (exif.debug) console.log("Not valid TIFF data! (no 0x002A)");
		return false;
	}

	const firstIFDOffset = file.getUint32(tiffOffset + 4, !bigEnd);

	if (firstIFDOffset < 0x00000008) {
		if (exif.debug) console.log("Not valid TIFF data! (First offset less than 8)", file.getUint32(tiffOffset + 4,
			!bigEnd));
		return false;
	}

	tags = readTags(file, tiffOffset, tiffOffset + firstIFDOffset, TiffTags, bigEnd);

	if (tags.ExifIFDPointer) {
		exifData = readTags(file, tiffOffset, tiffOffset + tags.ExifIFDPointer, ExifTags, bigEnd);
		for (tag in exifData) {
			switch (tag) {
				case "LightSource":
				case "Flash":
				case "MeteringMode":
				case "ExposureProgram":
				case "SensingMethod":
				case "SceneCaptureType":
				case "SceneType":
				case "CustomRendered":
				case "WhiteBalance":
				case "GainControl":
				case "Contrast":
				case "Saturation":
				case "Sharpness":
				case "SubjectDistanceRange":
				case "FileSource":
					exifData[tag] = StringValues[tag][exifData[tag]];
					break;

				case "ExifVersion":
				case "FlashpixVersion":
					exifData[tag] = String.fromCharCode(exifData[tag][0], exifData[tag][1], exifData[tag][2],
						exifData[tag][3]);
					break;

				case "ComponentsConfiguration":
					exifData[tag] =
						StringValues.Components[exifData[tag][0]] +
						StringValues.Components[exifData[tag][1]] +
						StringValues.Components[exifData[tag][2]] +
						StringValues.Components[exifData[tag][3]];
					break;
			}
			tags[tag] = exifData[tag];
		}
	}

	if (tags.GPSInfoIFDPointer) {
		gpsData = readTags(file, tiffOffset, tiffOffset + tags.GPSInfoIFDPointer, GPSTags, bigEnd);
		for (tag in gpsData) {
			switch (tag) {
				case "GPSVersionID":
					gpsData[tag] = gpsData[tag][0] +
						"." + gpsData[tag][1] +
						"." + gpsData[tag][2] +
						"." + gpsData[tag][3];
					break;
			}
			tags[tag] = gpsData[tag];
		}
	}

	// extract thumbnail
	tags['thumbnail'] = readThumbnailImage(file, tiffOffset, firstIFDOffset, bigEnd);

	return tags;
}

function findXMPinJPEG(file: ArrayBuffer) {

	if (!('DOMParser' in self)) {
		// console.warn('XML parsing not supported without DOMParser');
		return;
	}
	const dataView = new DataView(file);

	if (exif.debug) console.log("Got file of length " + file.byteLength);
	if ((dataView.getUint8(0) != 0xFF) || (dataView.getUint8(1) != 0xD8)) {
		if (exif.debug) console.log("Not a valid JPEG");
		return false; // not a valid jpeg
	}

	let offset = 2,
		length = file.byteLength,
		dom = new DOMParser();

	while (offset < (length - 4)) {
		if (getStringFromDB(dataView, offset, 4) == "http") {
			const startOffset = offset - 1;
			const sectionLength = dataView.getUint16(offset - 2) - 1;
			let xmpString = getStringFromDB(dataView, startOffset, sectionLength)
			const xmpEndIndex = xmpString.indexOf('xmpmeta>') + 8;
			xmpString = xmpString.substring(xmpString.indexOf('<x:xmpmeta'), xmpEndIndex);

			const indexOfXmp = xmpString.indexOf('x:xmpmeta') + 10
			//Many custom written programs embed xmp/xml without any namespace. Following are some of them.
			//Without these namespaces, XML is thought to be invalid by parsers
			xmpString = xmpString.slice(0, indexOfXmp) +
				'xmlns:Iptc4xmpCore="http://iptc.org/std/Iptc4xmpCore/1.0/xmlns/" ' +
				'xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" ' +
				'xmlns:tiff="http://ns.adobe.com/tiff/1.0/" ' +
				'xmlns:plus="http://schemas.android.com/apk/lib/com.google.android.gms.plus" ' +
				'xmlns:ext="http://www.gettyimages.com/xsltExtension/1.0" ' +
				'xmlns:exif="http://ns.adobe.com/exif/1.0/" ' +
				'xmlns:stEvt="http://ns.adobe.com/xap/1.0/sType/ResourceEvent#" ' +
				'xmlns:stRef="http://ns.adobe.com/xap/1.0/sType/ResourceRef#" ' +
				'xmlns:crs="http://ns.adobe.com/camera-raw-settings/1.0/" ' +
				'xmlns:xapGImg="http://ns.adobe.com/xap/1.0/g/img/" ' +
				'xmlns:Iptc4xmpExt="http://iptc.org/std/Iptc4xmpExt/2008-02-29/" ' +
				xmpString.slice(indexOfXmp)

			var domDocument = dom.parseFromString(xmpString, 'text/xml');
			return xml2Object(domDocument);
		} else {
			offset++;
		}
	}
}


function xml2json(xml: any) {
	var json = {};

	if (xml.nodeType == 1) { // element node
		if (xml.attributes.length > 0) {
			json['@attributes'] = {};
			for (var j = 0; j < xml.attributes.length; j++) {
				var attribute = xml.attributes.item(j);
				json['@attributes'][attribute.nodeName] = attribute.nodeValue;
			}
		}
	} else if (xml.nodeType == 3) { // text node
		return xml.nodeValue;
	}

	// deal with children
	if (xml.hasChildNodes()) {
		for (var i = 0; i < xml.childNodes.length; i++) {
			var child = xml.childNodes.item(i);
			var nodeName = child.nodeName;
			if (json[nodeName] == null) {
				json[nodeName] = xml2json(child);
			} else {
				if (json[nodeName].push == null) {
					var old = json[nodeName];
					json[nodeName] = [];
					json[nodeName].push(old);
				}
				json[nodeName].push(xml2json(child));
			}
		}
	}

	return json;
}

function xml2Object(xml: any) {
	try {
		var obj = {};
		if (xml.children.length > 0) {
			for (var i = 0; i < xml.children.length; i++) {
				var item = xml.children.item(i);
				var attributes = item.attributes;
				for (var idx in attributes) {
					var itemAtt = attributes[idx];
					var dataKey = itemAtt.nodeName;
					var dataValue = itemAtt.nodeValue;

					if (dataKey !== undefined) {
						obj[dataKey] = dataValue;
					}
				}
				var nodeName = item.nodeName;

				if (typeof (obj[nodeName]) == "undefined") {
					obj[nodeName] = xml2json(item);
				} else {
					if (typeof (obj[nodeName].push) == "undefined") {
						var old = obj[nodeName];

						obj[nodeName] = [];
						obj[nodeName].push(old);
					}
					obj[nodeName].push(xml2json(item));
				}
			}
		} else {
			obj = xml.textContent;
		}
		return obj;
	} catch (e) {
		console.log(e.message);
	}
}