如何从下载的图像中获取Exif数据

Question

在我的应用程序中，我需要从特定的URL链接下载图像并将其分配给UIImageView。我没有将该图像存储到我的库中，在这种情况下，如何在我的应用中获取此图像的 Exif数据（如EXIF_TAG_CREATE_DATE，EXIF_TAG_ARTIST等） ？

Answer 1

通过ImageIO访问图像属性，例如图像高度和宽度，DPI，EXIF数据等

CFURLRef url = CFURLCreateFromFileSystemRepresentation (kCFAllocatorDefault, (const UInt8 *)inputFileName, strlen(inputFileName), false);

if (!url) {
   printf ("* * Bad input file path\n"); 
}

CGImageSourceRef myImageSource;

myImageSource = CGImageSourceCreateWithURL(url, NULL);

CFDictionaryRef imagePropertiesDictionary;

imagePropertiesDictionary = CGImageSourceCopyPropertiesAtIndex(myImageSource,0, NULL);

CFNumberRef imageWidth = (CFNumberRef)CFDictionaryGetValue(imagePropertiesDictionary, kCGImagePropertyPixelWidth);
CFNumberRef imageHeight = (CFNumberRef)CFDictionaryGetValue(imagePropertiesDictionary, kCGImagePropertyPixelHeight);

int w = 0;
int h = 0;

CFNumberGetValue(imageWidth, kCFNumberIntType, &w);
CFNumberGetValue(imageHeight, kCFNumberIntType, &h);

CFRelease(imagePropertiesDictionary);
CFRelease(myImageSource);

printf("Image Width: %d\n",w);
printf("Image Height: %d\n",h);

（来源：http://developer.apple.com/library/ios/#qa/qa1654/_index.html）

    NSString *myPath = [[NSBundle mainBundle] pathForResource:@"IMG_2733" ofType:@"JPG"];
    NSURL *myURL = [NSURL fileURLWithPath:myPath];
    CGImageSourceRef mySourceRef = CGImageSourceCreateWithURL((CFURLRef)myURL, NULL);
    NSDictionary *myMetadata = (NSDictionary *) CGImageSourceCopyPropertiesAtIndex(mySourceRef,0,NULL);
    NSDictionary *exifDic = [myMetadata objectForKey:(NSString *)kCGImagePropertyExifDictionary];
    NSDictionary *tiffDic = [myMetadata objectForKey:(NSString *)kCGImagePropertyTIFFDictionary];
    NSLog(@"exifDic properties: %@", myMetadata); //all data
    float rawShutterSpeed = [[exifDic objectForKey:(NSString *)kCGImagePropertyExifExposureTime] floatValue];
    int decShutterSpeed = (1 / rawShutterSpeed);
    NSLog(@"Camera %@",[tiffDic objectForKey:(NSString *)kCGImagePropertyTIFFModel]);
    NSLog(@"Focal Length %@mm",[exifDic objectForKey:(NSString *)kCGImagePropertyExifFocalLength]);
    NSLog(@"Shutter Speed %@", [NSString stringWithFormat:@"1/%d", decShutterSpeed]);
    NSLog(@"Aperture f/%@",[exifDic objectForKey:(NSString *)kCGImagePropertyExifFNumber]);
    NSNumber *ExifISOSpeed  = [[exifDic objectForKey:(NSString*)kCGImagePropertyExifISOSpeedRatings] objectAtIndex:0];
    NSLog(@"ISO %i",[ExifISOSpeed integerValue]);
    NSLog(@"Taken %@",[exifDic objectForKey:(NSString*)kCGImagePropertyExifDateTimeDigitized]);

（来源：http://blog.depicus.com/index.php/2011/05/07/getting-exif-data-from-images-on-ios/）

通过开源（但过时的）iphone-exif库访问EXIF属性

NSData* theImageData = UIImageRepresentation(anImage,1.0);
EXFJpeg* jpegScanner = [[EXFJpeg alloc] init];
[jpegScanner scanImageData: theImageData];
EXFMetaData* exifData = jpegScanner.exifMetaData; EXFJFIF* jfif =
jpegScanner.jfif;
id tagValue = [exifData tagValue: aTagId];

（来源：http://code.google.com/p/iphone-exif/）

Answer 2

try this  

NSError *error = nil;
NSDictionary *attributes = [[NSFileManager defaultManager] 
    attributesOfItemAtPath:@"imagePath" error:&error];

if (!error) 
{
    NSLog(@"file attributes : %@",attributes);
}

and this is the result :

NSFileCreationDate = "2013-05-28 09:29:37 +0000";
NSFileExtensionHidden = 0;
NSFileGroupOwnerAccountID = 20;
NSFileGroupOwnerAccountName = staff;
NSFileModificationDate = "2013-05-28 09:29:37 +0000";
NSFileOwnerAccountID = 502;
NSFileOwnerAccountName = lerhan;
NSFilePosixPermissions = 420;
NSFileReferenceCount = 1;
NSFileSize = 1494;
NSFileSystemFileNumber = 46795419;
NSFileSystemNumber = 234881026;
NSFileType = NSFileTypeRegular;

to access any data type NSLog(@"file creation date : %@",[attributes objectForKey:@"NSFileCreationDate"]);