使用CGImageProperties获得EXIF属性 [英] Using CGImageProperties to get EXIF properties

问题描述

我希望能够在JPEG的元数据中添加文本注释，并能够从iphone应用程序中读回它.

I want to be able to add a text comment to the metadata of a JPEG and be able to read it back from within an iphone app.

我认为这很简单，因为ios4包含对EXIF信息的支持.因此，我使用一个名为usedAnalogExif的Windows工具添加了元数据，并使用以下命令从我的应用中读取了该数据:

I thought this would be fairly simple as ios4 contains support for EXIF info. So I added metadata using a Windows tool called used AnalogExif and read it back from my app using:

NSData *jpeg = UIImageJPEGRepresentation(myUIImage,1.0);

CGImageSourceRef  source = CGImageSourceCreateWithData((CFDataRef)jpeg, NULL);
NSDictionary *metadata = (NSDictionary *) CGImageSourceCopyPropertiesAtIndex(source,0,NULL);

NSMutableDictionary *metadataAsMutable = [[metadata mutableCopy]autorelease];
[metadata release];

NSMutableDictionary *EXIFDictionary = [[[metadataAsMutable objectForKey:(NSString *)kCGImagePropertyExifDictionary]

那行得通...到一个点:)

And that works...to a point :)

我在元数据字典中得到的内容类似于:

What I get back in the metadata dictionary is something like:

(gdb) po metadata
{
   ColorModel = RGB;
   Depth = 8;
   Orientation = 1;
   PixelHeight = 390;
   PixelWidth = 380;
   "{Exif}" =     {
      ColorSpace = 1;
      PixelXDimension = 380;
      PixelYDimension = 390;
   };
   "{JFIF}" =     {
      DensityUnit = 0;
      JFIFVersion = (
        1,
        1
      );
      XDensity = 1;
      YDensity = 1;
   };
   "{TIFF}" =     {
      Orientation = 1;
   };
}

但这就是我所能得到的！我已经使用可以找到的每个EXIF编辑器(大多数情况下应该是PC的)来编辑JPEG文件，尽管他们都说我已经添加了JPEG注释，EXIF标题和关键字，但是这些信息似乎都无法从Apple SDK中获得.在我的应用中.

But thats all I can get! I've edited the JPEG file with every EXIF editor I can find (mostly PC ones I should say) and although they all say I have added JPEG comments and EXIF captions and keywords, none of that info seems to be available from the Apple SDK in my app.

是否有人设法在jpeg的元数据中设置一个文本字段，并设法从iPhone应用程序中读取该文本字段?

Has anyone managed to set a text field in the metadata of a jpeg and manage to read it back from an iphone app?

我根本不想使用第三方库

I didn't want to use a third party library if at all possible

非常感谢

推荐答案

您认为iOS确实比您所看到的支持更多的元数据是正确的.创建UIImage并将其转换回JPEG时，可能会丢失数据.尝试NSData *jpeg = [NSData dataWithContentsOfFile:@"foo.jpg"]，您应该会看到EXIF.

You're correct in thinking that iOS does support more metadata than what you're seeing. You probably lost the data when you created a UIImage and then converted it back to JPEG. Try NSData *jpeg = [NSData dataWithContentsOfFile:@"foo.jpg"] and you should see the EXIF.

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