在 ALAssetRepresentation 中解释 XMP 元数据

Question

当用户对 iOS 内置 Photos.app 中的照片进行一些更改（裁剪、消除红眼等）时，这些更改不会应用到 @987654322 @ 由对应的ALAssetRepresentation 返回。

但是，更改将应用​​于thumbnail 和ALAssetRepresentation 返回的fullScreenImage。 此外，可以通过键 @"AdjustmentXMP" 在 ALAssetRepresentation 的元数据字典中找到有关已应用更改的信息。

我想自己将这些更改应用到fullResolutionImage 以保持一致性。我发现在 iOS6+ 上 CIFilter 的 filterArrayFromSerializedXMP: inputImageExtent:error: 可以将此 XMP 元数据转换为 CIFilter 的数组：

ALAssetRepresentation *rep; 
NSString *xmpString = rep.metadata[@"AdjustmentXMP"];
NSData *xmpData = [xmpString dataUsingEncoding:NSUTF8StringEncoding];

CIImage *image = [CIImage imageWithCGImage:rep.fullResolutionImage];

NSError *error = nil;
NSArray *filterArray = [CIFilter filterArrayFromSerializedXMP:xmpData 
                                             inputImageExtent:image.extent 
                                                        error:&error];
if (error) {
     NSLog(@"Error during CIFilter creation: %@", [error localizedDescription]);
}

CIContext *context = [CIContext contextWithOptions:nil];

for (CIFilter *filter in filterArray) {
     [filter setValue:image forKey:kCIInputImageKey];
     image = [filter outputImage];
}

但是，这仅适用于某些滤镜（裁剪、自动增强），但不适用于其他滤镜，例如去除红眼。在这些情况下，CIFilters 没有明显的效果。因此，我的问题：

• 有谁知道消除红眼的方法CIFilter？ （以与Photos.app一致的方式。带有kCIImageAutoAdjustRedEye键的过滤器是不够的。例如，它不接受眼睛位置的参数。）
• 是否有可能在 iOS 5 下生成和应用这些过滤器？

Answer 1

ALAssetRepresentation* representation = [[self assetAtIndex:index] defaultRepresentation];

// Create a buffer to hold the data for the asset's image
uint8_t *buffer = (Byte*)malloc(representation.size); // Copy the data from the asset into the buffer
NSUInteger length = [representation getBytes:buffer fromOffset: 0.0  length:representation.size error:nil];

if (length==0)
    return nil;

// Convert the buffer into a NSData object, and free the buffer after.

NSData *adata = [[NSData alloc] initWithBytesNoCopy:buffer length:representation.size freeWhenDone:YES];

// Set up a dictionary with a UTI hint. The UTI hint identifies the type
// of image we are dealing with (that is, a jpeg, png, or a possible
// RAW file).

// Specify the source hint.

NSDictionary* 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.

CGImageSourceRef sourceRef = CGImageSourceCreateWithData((CFDataRef) adata,  (CFDictionaryRef) sourceOptionsDict);

[adata release];

CFDictionaryRef imagePropertiesDictionary;

// Get a copy of the image properties from the CGImageSourceRef.

imagePropertiesDictionary = CGImageSourceCopyPropertiesAtIndex(sourceRef,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);

// Clean up memory

CFRelease(imagePropertiesDictionary);