iOS中上傳包含EXIF的圖片和修改圖片EXIF信息

很多小伙伴瀏覽圖片網(wǎng)站的時(shí)候,會(huì)發(fā)現(xiàn)圖片的一些拍攝參數(shù),包括光圈、像素、鏡頭、相機(jī)等,這些信息就是EXIF信息。

什么是EXIF

EXIF(Exchangeable Image File)是“可交換圖像文件”的縮寫,當(dāng)中包含了專門為數(shù)碼相機(jī)的照片而定制的元數(shù)據(jù),可以記錄數(shù)碼照片的拍攝參數(shù)、縮略圖及其他屬性信息。Exif標(biāo)準(zhǔn)最初由日本電子工業(yè)發(fā)展協(xié)會(huì)(JEIDA - Japan Electronic Industry Development Association)制訂,目前的最新版本是發(fā)布于2010年04月的 Exif 2.3 版,該版本曾在2012年12月以及2013年5月有所修正,并已經(jīng)應(yīng)用到各個(gè)廠商的新影像設(shè)備中。
簡(jiǎn)單來(lái)說(shuō),Exif 信息就是由數(shù)碼相機(jī)在拍攝過(guò)程中采集一系列的信息,然后把信息放置在我們熟知的 JPEG/TIFF 文件的頭部,也就是說(shuō) Exif信息是鑲嵌在 JPEG/TIFF 圖像文件格式內(nèi)的一組拍攝參數(shù),它就好像是傻瓜相機(jī)的日期打印功能一樣,只不過(guò) Exif信息所記錄的資訊更為詳盡和完備。Exif 所記錄的元數(shù)據(jù)信息非常豐富,主要包含了以下幾類信息:

  • 拍攝日期
  • 拍攝器材(機(jī)身、鏡頭、閃光燈等)
  • 拍攝參數(shù)(快門速度、光圈F值、ISO速度、焦距、測(cè)光模式等)
  • 圖像處理參數(shù)(銳化、對(duì)比度、飽和度、白平衡等)
  • 圖像描述及版權(quán)信息
  • GPS定位數(shù)據(jù)
  • 縮略圖

EXIF標(biāo)簽


iOS中如何取得圖片的EXIF信息

要取得EXIF信息,首先要獲取到圖片的原始數(shù)據(jù)。iOS是通過(guò)UIImagePickerController這個(gè)類來(lái)獲取圖片的,下面我們就通過(guò)代碼來(lái)說(shuō)明。

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info

{
    UIImage* tmpHeaderImg = [info objectForKey:UIImagePickerControllerEditedImage];
    NSURL *fileUrl = [info objectForKey:UIImagePickerControllerImageURL];
    //有的圖片選擇器返回的key是PHImageFileURLKey
    CGImageSourceRef imageSource = CGImageSourceCreateWithURL((CFURLRef)fileUrl, NULL);
    CFDictionaryRef imageInfo = CGImageSourceCopyPropertiesAtIndex(imageSource, 0,NULL);
    //imageInfo 為圖片全部EXIF信息 
    [self.image setImage:tmpHeaderImg];

}

代碼寫到這里用模擬器測(cè)試會(huì)發(fā)現(xiàn),能獲得圖片的EXIF信息,但是一用真機(jī)運(yùn)行就崩潰,這是為什么呢?
大家都知道,iOS上的APP只能取到沙盒里面的數(shù)據(jù),而PHImageFileURLKey給出的地址是圖片在手機(jī)里面的存儲(chǔ)地址,APP是沒(méi)有權(quán)限獲取的。這時(shí)候我們就要用Asset來(lái)獲取原始圖片數(shù)據(jù)

[[PHImageManager defaultManager] requestImageDataForAsset:asset options:nil resultHandler:^(NSData * _Nullable imageData, NSString * _Nullable dataUTI, UIImageOrientation orientation, NSDictionary * _Nullable info) {
            
   CGImageSourceRef imageSource = CGImageSourceCreateWithData((__bridge CFDataRef)imageData, NULL);
   NSDictionary *imageInfo = (__bridge NSDictionary*)CGImageSourceCopyPropertiesAtIndex(imageSource, 0, NULL);
           
        }];

通過(guò)Asset獲取圖片適用于真機(jī)和模擬器,這樣想服務(wù)器上傳上述方法返回的imageData,就可以獲得含有EXIF信息的圖片了。如果不獲取圖片原始數(shù)據(jù)直接從圖片選擇器上傳圖片,蘋果或基于安全和隱私方面的考慮,會(huì)隱藏大部分的EXIF信息。

以下是上方圖片的EXIF信息
Printing description of imageInfo:
{
    ColorModel = RGB;
    DPIHeight = 72;
    DPIWidth = 72;
    Depth = 8;
    Orientation = 1;
    PixelHeight = 3456;
    PixelWidth = 5184;
    ProfileName = "sRGB IEC61966-2.1";
    "{ExifAux}" =     {
        AFInfo =         (
            "0.4895833",
            "0.7025463",
            "0.02083333",
            "0.02488426",
            n,
            "0.3256173",
            "0.598235",
            "0.01697531",
            "0.03096065",
            n,
            "0.6574074",
            "0.598235",
            "0.01697531",
            "0.03096065",
            n,
            "0.2276234",
            "0.4845197",
            "0.01697531",
            "0.03096065",
            n,
            "0.4875579",
            "0.4810475",
            "0.02488426",
            "0.03790509",
            F,
            "0.7554013",
            "0.4845197",
            "0.01697531",
            "0.03096065",
            n,
            "0.3256173",
            "0.3708044",
            "0.01697531",
            "0.03096065",
            n,
            "0.6574074",
            "0.3708044",
            "0.01697531",
            "0.03096065",
            n,
            "0.4895833",
            "0.2725694",
            "0.02083333",
            "0.02488426",
            n
        );
        Firmware = "Firmware Version 1.1.1";
        FlashCompensation = 0;
        FocusMode = 1;
        ImageStabilization = 3;
        LensID = 51;
        LensInfo =         (
            18,
            135,
            0,
            0,
            18,
            135,
            0,
            0
        );
        LensModel = "Canon EF-S 18-135mm f/3.5-5.6 IS";
        SerialNumber = 331505805;
    };
    "{Exif}" =     {
        ApertureValue = 5;
        BodySerialNumber = 0331505805;
        ColorSpace = 1;
        ComponentsConfiguration =         (
            1,
            2,
            3,
            0
        );
        CustomRendered = 0;
        DateTimeDigitized = "2017:04:04 10:09:52";
        DateTimeOriginal = "2017:04:04 10:09:52";
        ExifVersion =         (
            2,
            3
        );
        ExposureBiasValue = 0;
        ExposureMode = 0;
        ExposureProgram = 3;
        ExposureTime = "0.01";
        FNumber = "5.6";
        Flash = 16;
        FlashPixVersion =         (
            1,
            0
        );
        FocalLength = 135;
        FocalPlaneResolutionUnit = 2;
        FocalPlaneXResolution = "5728.176470588235";
        FocalPlaneYResolution = "5808.403508771929";
        ISOSpeedRatings =         (
            100
        );
        LensModel = "EF-S18-135mm f/3.5-5.6 IS";
        LensSerialNumber = 000012e3b8;
        LensSpecification =         (
            18,
            135,
            0,
            0
        );
        MaxApertureValue = "5.656853725850966";
        MeteringMode = 5;
        PixelXDimension = 5184;
        PixelYDimension = 3456;
        RecommendedExposureIndex = 100;
        SceneCaptureType = 0;
        SensitivityType = 2;
        ShutterSpeedValue = "6.625";
        SubsecTime = 00;
        SubsecTimeDigitized = 00;
        SubsecTimeOriginal = 00;
        WhiteBalance = 0;
    };
    "{IPTC}" =     {
        Byline =         (
            ""
        );
        CopyrightNotice = "";
        StarRating = 0;
    };
    "{MakerCanon}" =     {
        CameraTemperatur = 15;
        ContinuousDrive = 0;
        FocusDistanceLower = "1.66";
        FocusDistanceUpper = "1.82";
        LensModel = "EF-S18-135mm f/3.5-5.6 IS";
        MaxAperture = "5.656854249492381";
        MinAperture = "35.91878554589994";
        UniqueModelID = 2147484295;
        WhiteBalanceIndex = 0;
    };
    "{PictureStyle}" =     {
        ColorTone =         (
            0,
            0,
            0
        );
        Monochrome =         (
            0,
            0,
            0
        );
        PictStyleColorSpace =         (
            sRGB,
            1,
            1
        );
        PictureStyle =         (
            4095,
            4095,
            4095
        );
        SharpnessFreq =         (
            0,
            0,
            0
        );
    };
    "{TIFF}" =     {
        Artist = "";
        Copyright = "";
        DateTime = "2017:04:04 10:09:52";
        Make = Canon;
        Model = "Canon EOS 60D";
        Orientation = 1;
        ResolutionUnit = 2;
        XResolution = 72;
        YResolution = 72;
    };
}

如何修改圖片的EXIF

  1. 獲取圖片中的EXIF文件
NSMutableDictionary *metaDataDic = [imageInfo mutableCopy];
NSMutableDictionary *exifDic =[[metaDataDic objectForKey:(NSString*)kCGImagePropertyExifDictionary]mutableCopy];
  1. 修改EXIF文件中的部分信息
[exifDic setObject:[NSNumber numberWithFloat:123123] forKey:(NSString *)kCGImagePropertyExifExposureTime];
[exifDic setObject:@"SenseTime" forKey:(NSString *)kCGImagePropertyExifLensModel];

[metaDataDic setObject:exifDic forKey:(NSString*)kCGImagePropertyExifDictionary];
  1. 將修改后的文件寫入至圖片中
CFStringRef UTI = CGImageSourceGetType(imageSource);
NSMutableData *newImageData = [NSMutableData data];
CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)newImageData, UTI, 1,NULL);

//add the image contained in the image source to the destination, overidding the old metadata with our modified metadata
CGImageDestinationAddImageFromSource(destination, source, 0, (__bridge CFDictionaryRef)metaDataDic);
CGImageDestinationFinalize(destination);
  1. 保存圖片
NSString *directoryDocuments =  NSTemporaryDirectory();
[newImageData writeToFile: directoryDocuments atomically:YES];
  1. 查看修改后圖片的Exif信息
CIImage *testImage = [CIImage imageWithData:newImageData];
NSDictionary *propDict = [testImage properties];
NSLog(@"Properties %@", propDict);

注意事項(xiàng)

關(guān)于無(wú)法修改Exif值的幾點(diǎn)注意事項(xiàng):

  1. 傳入的數(shù)據(jù)格式與Exif規(guī)定的不符
    Exif的每條信息都有對(duì)應(yīng)的數(shù)據(jù)類型,如:String Float... 如果數(shù)據(jù)類型傳入錯(cuò)誤將無(wú)法寫入文件。
  2. 傳入的字段超過(guò)規(guī)定字段長(zhǎng)度
  3. 相互依賴的字段只添加了一個(gè)字段
    在GPS文件中經(jīng)緯度的度數(shù)的字段與經(jīng)緯度的方向的字段相互依賴,修改經(jīng)/緯度數(shù)需要經(jīng)/緯方向字段的存在,否則修改無(wú)效。

參考鏈接:http://www.lxweimin.com/p/a542751d4ba3

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