vue2.0调用摄像头步骤详解
2020-11-27
来源：华佗健康网
可以在github 上下载demo链接
vue组件代码
<template>
<p>
<p style="padding:20px;">
<p class="show">
<p class="picture" :style="'backgroundImage:url('+headerImage+')'"></p>
</p>
<p style="margin-top:20px;">
<input type="file" id="upload" accept="image/jpg" @change="upload">
<label for="upload"></label>
</p>
</p>
</p>
</template>
<script>
import {Exif} from './exif.js'
export default {
data () {
return {
headerImage:'',picValue:''
}
},
mounted () {
},
methods: {
upload (e) {
let files = e.target.files || e.dataTransfer.files;
if (!files.length) return;
this.picValue = files[0];
this.imgPreview(this.picValue);
console.log(this.picValue)
},
imgPreview (file) {
let self = this;
let Orientation;
//去获取拍照时的信息，解决拍出来的照片旋转问题
Exif.getData(file, function(){
Orientation = Exif.getTag(this, 'Orientation');
});
// 看支持不支持FileReader
if (!file || !window.FileReader) return;
if (/^image/.test(file.type)) {
// 创建一个reader
let reader = new FileReader();
// 将图片2将转成 base64 格式
reader.readAsDataURL(file);
// 读取成功后的回调
reader.onloadend = function () {
let result = this.result;
let img = new Image();
img.src = result;
//判断图片是否大于100K,是就直接上传，反之压缩图片
if (this.result.length <= (100 * 1024)) {
self.headerImage = this.result;
self.postImg();
}else {
img.onload = function () {
let data = self.compress(img,Orientation);
self.headerImage = data;
self.postImg();
}
}
}
}
},
postImg () {
//这里写接口
},
rotateImg (img, direction,canvas) {
//最小与最大旋转方向，图片旋转4次后回到原方向
const min_step = 0;
const max_step = 3;
if (img == null)return;
//img的高度和宽度不能在img元素隐藏后获取，否则会出错
let height = img.height;
let width = img.width;
let step = 2;
if (step == null) {
step = min_step;
}
if (direction == 'right') {
step++;
//旋转到原位置，即超过最大值
step > max_step && (step = min_step);
} else {
step--;
step < min_step && (step = max_step);
}
//旋转角度以弧度值为参数
let degree = step * 90 * Math.PI / 180;
let ctx = canvas.getContext('2d');
switch (step) {
case 0:
canvas.width = width;
canvas.height = height;
ctx.drawImage(img, 0, 0);
break;
case 1:
canvas.width = height;
canvas.height = width;
ctx.rotate(degree);
ctx.drawImage(img, 0, -height);
break;
case 2:
canvas.width = width;
canvas.height = height;
ctx.rotate(degree);
ctx.drawImage(img, -width, -height);
break;
case 3:
canvas.width = height;
canvas.height = width;
ctx.rotate(degree);
ctx.drawImage(img, -width, 0);
break;
}
},
compress(img,Orientation) {
let canvas = document.createElement("canvas");
let ctx = canvas.getContext('2d');
//瓦片canvas
let tCanvas = document.createElement("canvas");
let tctx = tCanvas.getContext("2d");
let initSize = img.src.length;
let width = img.width;
let height = img.height;
//如果图片大于四百万像素，计算压缩比并将大小压至400万以下
let ratio;
if ((ratio = width * height / 4000000) > 1) {
console.log("大于400万像素")
ratio = Math.sqrt(ratio);
width /= ratio;
height /= ratio;
} else {
ratio = 1;
}
canvas.width = width;
canvas.height = height;
// 铺底色
ctx.fillStyle = "#fff";
ctx.fillRect(0, 0, canvas.width, canvas.height);
//如果图片像素大于100万则使用瓦片绘制
let count;
if ((count = width * height / 1000000) > 1) {
console.log("超过100W像素");
count = ~~(Math.sqrt(count) + 1); //计算要分成多少块瓦片
// 计算每块瓦片的宽和高
let nw = ~~(width / count);
let nh = ~~(height / count);
tCanvas.width = nw;
tCanvas.height = nh;
for (let i = 0; i < count; i++) {
for (let j = 0; j < count; j++) {
tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh);
ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh);
}
}
} else {
ctx.drawImage(img, 0, 0, width, height);
}
//修复ios上传图片的时候 被旋转的问题
if(Orientation != "" && Orientation != 1){
switch(Orientation){
case 6://需要顺时针（向左）90度旋转
this.rotateImg(img,'left',canvas);
break;
case 8://需要逆时针（向右）90度旋转
this.rotateImg(img,'right',canvas);
break;
case 3://需要180度旋转
this.rotateImg(img,'right',canvas);//转两次
this.rotateImg(img,'right',canvas);
break;
}
}
//进行最小压缩
let ndata = canvas.toDataURL('image/jpeg', 0.1);
console.log('压缩前：' + initSize);
console.log('压缩后：' + ndata.length);
console.log('压缩率：' + ~~(100 * (initSize - ndata.length) / initSize) + "%");
tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0;
return ndata;
},
}
}
</script>
<style>
*{
margin: 0;
padding: 0;
}
.show {
width: 100px;
height: 100px;
overflow: hidden;
position: relative;
border-radius: 50%;
border: 1px solid #d5d5d5;
}
.picture {
width: 100%;
height: 100%;
overflow: hidden;
background-position: center center;
background-repeat: no-repeat;
background-size: cover;
}
</style>引用的exif.js代码
(function() {
var debug = false;
var root = this;
var EXIF = function(obj) {
if (obj instanceof EXIF) return obj;
if (!(this instanceof EXIF)) return new EXIF(obj);
this.EXIFwrapped = obj;
};
if (typeof exports !== 'undefined') {
if (typeof module !== 'undefined' && module.exports) {
exports = module.exports = EXIF;
}
exports.EXIF = EXIF;
} else {
root.EXIF = EXIF;
}
var ExifTags = EXIF.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
};
var TiffTags = EXIF.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"
};
var GPSTags = EXIF.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"
};
var StringValues = EXIF.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"
}
};
function addEvent(element, event, handler) {
if (element.addEventListener) {
element.addEventListener(event, handler, false);
} else if (element.attachEvent) {
element.attachEvent("on" + event, handler);
}
}
function imageHasData(img) {
return !!(img.exifdata);
}
function base64ToArrayBuffer(base64, contentType) {
contentType = contentType || base64.match(/^data\:([^\;]+)\;base64,/mi)[1] || ''; // e.g. 'data:image/jpeg;base64,...' => 'image/jpeg'
base64 = base64.replace(/^data\:([^\;]+)\;base64,/gmi, '');
var binary = atob(base64);
var len = binary.length;
var buffer = new ArrayBuffer(len);
var view = new Uint8Array(buffer);
for (var i = 0; i < len; i++) {
view[i] = binary.charCodeAt(i);
}
return buffer;
}
function objectURLToBlob(url, callback) {
var 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();
}
function getImageData(img, callback) {
function handleBinaryFile(binFile) {
var data = findEXIFinJPEG(binFile);
var iptcdata = findIPTCinJPEG(binFile);
img.exifdata = data || {};
img.iptcdata = iptcdata || {};
if (callback) {
callback.call(img);
}
}
if (img.src) {
if (/^data\:/i.test(img.src)) { // Data URI
var arrayBuffer = base64ToArrayBuffer(img.src);
handleBinaryFile(arrayBuffer);
} else if (/^blob\:/i.test(img.src)) { // Object URL
var fileReader = new FileReader();
fileReader.onload = function(e) {
handleBinaryFile(e.target.result);
};
objectURLToBlob(img.src, function (blob) {
fileReader.readAsArrayBuffer(blob);
});
} else {
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 if (window.FileReader && (img instanceof window.Blob || img instanceof window.File)) {
var fileReader = new FileReader();
fileReader.onload = function(e) {
if (debug) console.log("Got file of length " + e.target.result.byteLength);
handleBinaryFile(e.target.result);
};
fileReader.readAsArrayBuffer(img);
}
}
function findEXIFinJPEG(file) {
var dataView = new DataView(file);
if (debug) console.log("Got file of length " + file.byteLength);
if ((dataView.getUint8(0) != 0xFF) || (dataView.getUint8(1) != 0xD8)) {
if (debug) console.log("Not a valid JPEG");
return false; // not a valid jpeg
}
var offset = 2,
length = file.byteLength,
marker;
while (offset < length) {
if (dataView.getUint8(offset) != 0xFF) {
if (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 (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 (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) {
var dataView = new DataView(file);
if (debug) console.log("Got file of length " + file.byteLength);
if ((dataView.getUint8(0) != 0xFF) || (dataView.getUint8(1) != 0xD8)) {
if (debug) console.log("Not a valid JPEG");
return false; // not a valid jpeg
}
var offset = 2,
length = file.byteLength;
var isFieldSegmentStart = function(dataView, offset){
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++;
}
}
var IptcFieldMap = {
0x78 : 'caption',
0x6E : 'credit',
0x19 : 'keywords',
0x37 : 'dateCreated',
0x50 : 'byline',
0x55 : 'bylineTitle',
0x7A : 'captionWriter',
0x69 : 'headline',
0x74 : 'copyright',
0x0F : 'category'
};
function readIPTCData(file, startOffset, sectionLength){
var dataView = new DataView(file);
var data = {};
var fieldValue, fieldName, dataSize, segmentType, segmentSize;
var 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, tiffStart, dirStart, strings, bigEnd) {
var entries = file.getUint16(dirStart, !bigEnd),
tags = {},
entryOffset, tag,
i;
for (i=0;i<entries;i++) {
entryOffset = dirStart + i*12 + 2;
tag = strings[file.getUint16(entryOffset, !bigEnd)];
if (!tag && debug) console.log("Unknown tag: " + file.getUint16(entryOffset, !bigEnd));
tags[tag] = readTagValue(file, entryOffset, tiffStart, dirStart, bigEnd);
}
return tags;
}
function readTagValue(file, entryOffset, tiffStart, dirStart, bigEnd) {
var 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;
}
}
}
function getStringFromDB(buffer, start, length) {
var outstr = "";
for (n = start; n < start+length; n++) {
outstr += String.fromCharCode(buffer.getUint8(n));
}
return outstr;
}
function readEXIFData(file, start) {
if (getStringFromDB(file, start, 4) != "Exif") {
if (debug) console.log("Not valid EXIF data! " + getStringFromDB(file, start, 4));
return false;
}
var 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 (debug) console.log("Not valid TIFF data! (no 0x4949 or 0x4D4D)");
return false;
}
if (file.getUint16(tiffOffset+2, !bigEnd) != 0x002A) {
if (debug) console.log("Not valid TIFF data! (no 0x002A)");
return false;
}
var firstIFDOffset = file.getUint32(tiffOffset+4, !bigEnd);
if (firstIFDOffset < 0x00000008) {
if (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];
}
}
return tags;
}
EXIF.getData = function(img, callback) {
if ((img instanceof Image || img instanceof HTMLImageElement) && !img.complete) return false;
if (!imageHasData(img)) {
getImageData(img, callback);
} else {
if (callback) {
callback.call(img);
}
}
return true;
}
EXIF.getTag = function(img, tag) {
if (!imageHasData(img)) return;
return img.exifdata[tag];
}
EXIF.getAllTags = function(img) {
if (!imageHasData(img)) return {};
var a,
data = img.exifdata,
tags = {};
for (a in data) {
if (data.hasOwnProperty(a)) {
tags[a] = data[a];
}
}
return tags;
}
EXIF.pretty = function(img) {
if (!imageHasData(img)) return "";
var 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;
}
EXIF.readFromBinaryFile = function(file) {
return findEXIFinJPEG(file);
}
if (typeof define === 'function' && define.amd) {
define('exif-js', [], function() {
return EXIF;
});
}
}.call(this));相信看了本文案例你已经掌握了方法，更多精彩请关注Gxl网其它相关文章！
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