{"id":24,"date":"2012-07-12T15:13:09","date_gmt":"2012-07-12T07:13:09","guid":{"rendered":"http:\/\/hmu023267.chinaw3.com\/wordpress\/?p=24"},"modified":"2012-07-12T15:13:09","modified_gmt":"2012-07-12T07:13:09","slug":"ios-exif%e7%9b%b8%e5%85%b3%e6%96%87%e7%ab%a0","status":"publish","type":"post","link":"https:\/\/www.sunyuping.com\/index.php\/2012\/07\/12\/ios-exif%e7%9b%b8%e5%85%b3%e6%96%87%e7%ab%a0\/","title":{"rendered":"ios exif\u76f8\u5173\u6587\u7ae0"},"content":{"rendered":"
\n

<\/h2>\n<\/div>\n
\n

1.ALAssetRepresentation* representation = [[self assetAtIndex:index] defaultRepresentation];\/\/ create a buffer to hold the data for the asset’s image<\/p>\n

uint8_t *buffer = (Byte*)malloc(representation.size);\/\/ copy the data from the asset into the buffer
\nNSUInteger length = [representation getBytes:buffer fromOffset: 0.0 length:representation.size error:nil];
\nif (length==0) return nil;\/\/ convert the buffer into a NSData object, free the buffer after
\nNSData *adata = [[NSData alloc] initWithBytesNoCopy:buffer length:representation.size freeWhenDone:YES];\/\/ setup a dictionary with a UTI hint. The UTI hint identifies the type of image we are dealing with (ie. a jpeg, png, or a possible RAW file)\/\/ specify the source hint
\nNSDictionary* sourceOptionsDict = [NSDictionary dictionaryWithObjectsAndKeys:(id)[representation UTI] ,kCGImageSourceTypeIdentifierHint,nil];\/\/ create a CGImageSource with the NSData. A image source can contain x number of thumbnails and full images.
\nCGImageSourceRef sourceRef = CGImageSourceCreateWithData((CFDataRef) adata, (CFDictionaryRef) sourceOptionsDict);
\n[adata release];
\nCFDictionaryRef imagePropertiesDictionary;\/\/ get a copy of the image properties from the CGImageSourceRef
\nimagePropertiesDictionary = CGImageSourceCopyPropertiesAtIndex(sourceRef,0, NULL);
\nCFNumberRef imageWidth = (CFNumberRef)CFDictionaryGetValue(imagePropertiesDictionary, kCGImagePropertyPixelWidth);
\nCFNumberRef imageHeight = (CFNumberRef)CFDictionaryGetValue(imagePropertiesDictionary, kCGImagePropertyPixelHeight);
\nint w = 0;int h = 0;CFNumberGetValue(imageWidth, kCFNumberIntType, &w);
\nCFNumberGetValue(imageHeight, kCFNumberIntType, &h);
\n\/\/ cleanup memory
\nCFRelease(imagePropertiesDictionary);
\nCFRelease(sourceRef);<\/p>\n

——————————————————————————————————————————————-<\/p>\n

2.
\n <\/p>\n

The API has changed the rules slightly and you dont get direct file system access to the iPhoto library any more. Instead you get asset library URL’s like this.<\/p>\n

assets-library:\/\/asset\/asset.JPG?id=1000000003&ext=JPG<\/p>\n

You use the ALAssetLibrary object to access the ALAsset object via the URL.<\/p>\n

so from the docs for ALAssetLibrary throw this in a header (or your source)<\/p>\n

typedefvoid(^ALAssetsLibraryAssetForURLResultBlock)(ALAsset*asset);
\ntypedefvoid(^ALAssetsLibraryAccessFailureBlock)(NSError*error);
\nwhich isnt strictly needed but keeps things pretty.
\nand then in your source.<\/p>\n

-(void)findLargeImage
\n{
\nNSString*mediaurl =[self.node valueForKey:kVMMediaURL];<\/p>\n

\/\/
\nALAssetsLibraryAssetForURLResultBlock resultblock =^(ALAsset*myasset)
\n{
\nALAssetRepresentation*rep =[myasset defaultRepresentation];
\nCGImageRef iref =[rep fullResolutionImage];
\nif(iref){
\nlargeimage =[UIImage imageWithCGImage:iref];
\n[largeimage retain];
\n}
\n};<\/p>\n

\/\/
\nALAssetsLibraryAccessFailureBlock failureblock \u00a0=^(NSError*myerror)
\n{
\nNSLog(@”booya, cant get image – %@”,[myerror localizedDescription]);
\n};<\/p>\n

if(mediaurl &&[mediaurl length]&&![[mediaurl pathExtension] isEqualToString:AUDIO_EXTENSION])
\n{
\n[largeimage release];
\nNSURL *asseturl =[NSURL URLWithString:mediaurl];
\nALAssetsLibrary* assetslibrary =[[[ALAssetsLibrary alloc] init] autorelease];
\n[assetslibrary assetForURL:asseturl
\nresultBlock:resultblock
\nfailureBlock:failureblock];
\n}
\n}
\nA couple of things to note are that this uses blocks which were new to me before I started my iOS4 porting but you might like to look at<\/p>\n

http:\/\/www.mikeash.com\/pyblog\/friday-qa-2008-12-26.html<\/a><\/p>\n

and<\/p>\n

http:\/\/developer.apple.com\/library\/ios\/#documentation\/Cocoa\/Conceptual\/Blocks\/Articles\/00_Introduction.html<\/a><\/p>\n

They bend your head a little but if you think of them as notification selectors or callbacks it kind of helps.<\/p>\n

Also<\/p>\n