我想查找从iPhone/iPad相机拍摄的图像的DPI这就是我尝试获取DPI的方式CFDictionaryRefexifDict=CMGetAttachment(imageDataSampleBuffer,kCGImagePropertyExifDictionary,NULL);originalExifDict=(__bridgeNSMutableDictionary*)(exifDict);[originalExifDictobjectForKey:(NSString*)kCGImagePropertyDPIHeight][originalExifDictobjectForKey:(