用iphone拍的照片，有照片的位置信息，该信息存在与jpeg格式的exit信息中，也并不是苹果公司的原创。其实就是图片文件存储空间中，有一个区域是专门存储附加信息的，比如光圈、快门、日期等等，其实信息量也蛮大的，地理位置信息就是其中一组以gps开头的信息。当然，我们一般使用的图片编辑工具会忽略掉该信息，也就是说iphone拍的照片在使用平常windows下的照片编辑器后可能会丢失该信息。
要读取exit信息，其实就是加载图片文件后，以二进制读取文件中相应的偏移量，从而可以获得照片exif信息。这里查到一个js访问exit信息的脚本，还有一个C#访问exif的类。
通过javascript访问照片exit信息：
http://www.nihilogic.dk/labs/exif/exif.js
如果访问该url有问题，可以参考代码如下：
/\* \* Javascript EXIF Reader 0.1.4 \* Copyright (c) 2008 Jacob Seidelin, [email protected], http://blog.nihilogic.dk/ \* Licensed under the MPL License \[http://www.nihilogic.dk/licenses/mpl-license.txt\] \*/ var EXIF = {}; (function() { var bDebug = false; 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 }; EXIF.
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