使用AVFoundation framework获取图像时，如何在图像中保存自定义元数据？
我知道我可以访问属性天气，但我的图像为UIImage或CIImage，但是这些属性似乎彼此不同(即使它是同一图像)。
到目前为止，我像这样访问字典:(代码取自Caffeinated Cocoa博客)
NSLog(@"about to request a capture from: %@", [self stillImageOutput]);
[[self stillImageOutput] captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler:^(CMSampleBufferRef imageSampleBuffer, NSError *error)
{
NSData *jpeg = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer] ;
CGImageSourceRef source = CGImageSourceCreateWithData((__bridge_retained CFDataRef)jpeg, NULL);
//get all the metadata in the image
NSDictionary *metadata = (__bridge NSDictionary *) CGImageSourceCopyPropertiesAtIndex(source,0,NULL);
//make the metadata dictionary mutable so we can add properties to it
NSMutableDictionary *metadataAsMutable = [metadata mutableCopy];
NSMutableDictionary *EXIFDictionary = [[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyExifDictionary]mutableCopy];
NSMutableDictionary *GPSDictionary = [[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyGPSDictionary]mutableCopy];
NSMutableDictionary *RAWDictionary = [[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyRawDictionary]mutableCopy];
if(!EXIFDictionary) {
EXIFDictionary = [NSMutableDictionary dictionary];
}
if(!GPSDictionary) {
GPSDictionary = [NSMutableDictionary dictionary];
}
if(!RAWDictionary) {
RAWDictionary = [NSMutableDictionary dictionary];
}
float _lat = gpsInfo.coordinate.latitude;
float _lon = gpsInfo.coordinate.longitude;
float _alt = gpsInfo.altitude;
NSDate *_date = gpsInfo.timestamp;
float _heading = gpsInfo.course;;
[GPSDictionary setValue:[NSNumber numberWithFloat:_lat]
forKey:(NSString*)kCGImagePropertyGPSLatitude];
[GPSDictionary setValue:[NSNumber numberWithFloat:_lon]
forKey:(NSString*)kCGImagePropertyGPSLongitude];
[GPSDictionary setValue:[NSNumber numberWithFloat:_alt]
forKey:(NSString*)kCGImagePropertyGPSAltitude];
[GPSDictionary setValue:_date
forKey:(NSString*)kCGImagePropertyGPSDateStamp];
[GPSDictionary setValue:[NSNumber numberWithFloat:_heading]
forKey:(NSString*)kCGImagePropertyGPSImgDirection];
[EXIFDictionary setValue:@"Wasup" forKey:(NSString *)kCGImagePropertyExifUserComment];
[RAWDictionary setValue:attitude forKey:@"Attitude"];
//Add the modified Data back into the image’s metadata
[metadataAsMutable setObject:EXIFDictionary forKey:(NSString *)kCGImagePropertyExifDictionary];
[metadataAsMutable setObject:GPSDictionary forKey:(NSString *)kCGImagePropertyGPSDictionary];
[metadataAsMutable setObject:RAWDictionary forKey:(NSString *)kCGImagePropertyRawDictionary];
NSLog(@"Info: %@",metadataAsMutable);
CFStringRef UTI = CGImageSourceGetType(source); //this is the type of image (e.g., public.jpeg)
//this will be the data CGImageDestinationRef will write into
NSMutableData *data = [NSMutableData data];
CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)data,UTI,1,NULL);
if(!destination) {
NSLog(@"***Could not create image destination ***");
}
//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) metadataAsMutable);
//tell the destination to write the image data and metadata into our data object.
//It will return false if something goes wrong
BOOL success = NO;
success = CGImageDestinationFinalize(destination);
if(!success) {
NSLog(@"***Could not create data from image destination ***");
}
而且我可以这样保存我的图像:
CIImage *testImage = [CIImage imageWithData:data];
NSDictionary *propDict = [testImage properties];
NSLog(@"Properties %@",propDict);
或者像这样
UIImage *imageMod = [[UIImage alloc] initWithData:data];
CGImageSourceRef source2 = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
//get all the metadata in the image
NSDictionary *metadata2 = (__bridge NSDictionary *) CGImageSourceCopyPropertiesAtIndex(source2,0,NULL);
NSLog(@"WASD: %@",metadata2);
但是，这两个选项都不返回我的“自定义原始数据字典”。
总之，我想做的是将自己的对象保存在自己创建的字段中(在这种情况下为cmattitude对象)
PD:当我在将字典与图像合并之前对字典进行
NSLOG编码时，它确实具有我想要的所有文件。Info: {
ColorModel = RGB;
DPIHeight = 72;
DPIWidth = 72;
Depth = 8;
Orientation = 6;
PixelHeight = 1080;
PixelWidth = 1920;
"{Exif}" = {
ApertureValue = "2.526069";
BrightnessValue = "4.013361";
ColorSpace = 1;
ComponentsConfiguration = (
1,
2,
3,
0
);
ExifVersion = (
2,
2,
1
);
ExposureMode = 0;
ExposureProgram = 2;
ExposureTime = "0.03333334";
FNumber = "2.4";
Flash = 16;
FlashPixVersion = (
1,
0
);
FocalLenIn35mmFilm = 35;
FocalLength = "4.28";
ISOSpeedRatings = (
80
);
MeteringMode = 5;
PixelXDimension = 1920;
PixelYDimension = 1080;
SceneCaptureType = 0;
SensingMethod = 2;
Sharpness = 0;
ShutterSpeedValue = "4.906905";
SubjectArea = (
959,
539,
518,
388
);
UserComment = "Wazup";
WhiteBalance = 0;
};
"{GPS}" = {
Altitude = 102;
DateStamp = "2012-01-20 06:55:48 +0000";
ImgDirection = "-1";
Latitude = "35.02496";
Longitude = "135.754";
};
"{Raw}" = {
Attitude = "Pitch: 50.913760, Roll: 36.342350, Yaw: -164.272361 @ 0.048291\n";
};
"{TIFF}" = {
Orientation = 6;
ResolutionUnit = 2;
XResolution = 72;
YResolution = 72;
"_YCbCrPositioning" = 1;
};
但是，当我从新镜像中NSLOG字典时，它给了我CIIMage的信息:
Properties {
ColorModel = RGB;
DPIHeight = 72;
DPIWidth = 72;
Depth = 8;
Orientation = 6;
PixelHeight = 1080;
PixelWidth = 1920;
"{Exif}" = {
ApertureValue = "2.526069";
BrightnessValue = "4.013361";
ColorSpace = 1;
ComponentsConfiguration = (
0,
0,
0,
1
);
ExifVersion = (
2,
2,
1
);
ExposureMode = 0;
ExposureProgram = 2;
ExposureTime = "0.03333334";
FNumber = "2.4";
Flash = 16;
FlashPixVersion = (
1,
0
);
FocalLenIn35mmFilm = 35;
FocalLength = "4.28";
ISOSpeedRatings = (
80
);
MeteringMode = 5;
PixelXDimension = 1920;
PixelYDimension = 1080;
SceneCaptureType = 0;
SensingMethod = 2;
Sharpness = 0;
ShutterSpeedValue = "4.906905";
SubjectArea = (
959,
539,
518,
388
);
UserComment = "Wazup";
WhiteBalance = 0;
};
"{GPS}" = {
Altitude = 102;
ImgDirection = 0;
Latitude = "35.025";
Longitude = "135.754";
};
"{JFIF}" = {
DensityUnit = 1;
JFIFVersion = (
1,
1
);
XDensity = 72;
YDensity = 72;
};
"{TIFF}" = {
Orientation = 6;
ResolutionUnit = 2;
XResolution = 72;
YResolution = 72;
"_YCbCrPositioning" = 1;
};
如果我用
NSLog编码，它给我的信息更少。谢谢!
最佳答案
UIImage和CIImage并不保存所有元数据。实际上，将其从NSData转换为这两种格式中的任何一种都会去除大量的元数据，因此，仅当您计划在UI中显示它或将其传递给CoreImage时，才应使用IMHO，UIImage和CIImage。
您可以读取图像属性，如下所示:
- (NSDictionary *)getImageProperties:(NSData *)imageData {
// get the original image metadata
CGImageSourceRef imageSourceRef = CGImageSourceCreateWithData((__bridge CFDataRef) imageData, NULL);
CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(imageSourceRef, 0, NULL);
NSDictionary *props = (__bridge_transfer NSDictionary *) properties;
CFRelease(imageSourceRef);
return props;
}
然后，您可以将
NSDictionary转换为NSMutableDictionary:NSDictionary *props = [self getImageProperties:imageData];
NSMutableDictionary *mutableDictionary = [NSMutableDictionary dictionaryWithDictionary:props];
之后，添加您想要的任何字段。请注意，通过抓取
kCGImagePropertyExifDictionary，GPS数据和kCGImagePropertyGPSDictionary可以找到EXIF数据，依此类推:NSMutableDictionary *exifDictionary = properties[(__bridge NSString *) kCGImagePropertyExifDictionary];
查看
CGImageProperties头文件以获取所有可用的 key 。好的，现在您已经对元数据进行了所需的任何更改，将其添加回去需要执行更多的步骤:
// incoming image data
NSData *imageData;
// create the image ref
CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData((__bridge CFDataRef) imageData);
CGImageRef imageRef = CGImageCreateWithJPEGDataProvider(imgDataProvider, NULL, true, kCGRenderingIntentDefault);
// the updated properties from above
NSMutableDictionary *mutableDictionary;
// create the new output data
CFMutableDataRef newImageData = CFDataCreateMutable(NULL, 0);
// my code assumes JPEG type since the input is from the iOS device camera
CFStringRef type = UTTypeCreatePreferredIdentifierForTag(kUTTagClassMIMEType, (__bridge CFStringRef) @"image/jpg", kUTTypeImage);
// create the destination
CGImageDestinationRef destination = CGImageDestinationCreateWithData(newImageData, type, 1, NULL);
// add the image to the destination
CGImageDestinationAddImage(destination, imageRef, (__bridge CFDictionaryRef) mutableDictionary);
// finalize the write
CGImageDestinationFinalize(destination);
// memory cleanup
CGDataProviderRelease(imgDataProvider);
CGImageRelease(imageRef);
CFRelease(type);
CFRelease(destination);
// your new image data
NSData *newImage = (__bridge_transfer NSData *)newImageData;
在那里，您拥有了它。