转载自:http://blog.sina.com.cn/s/blog_61235faa0100z3dp.html
CIImage *saveToSave = [filter outputImage]; CGImageRef cgImg = [context createCGImage:saveToSave fromRect:[saveToSave extent]];
ALAssetsLibrary* library = [[ALAssetsLibrary alloc] init];
[library writeImageToSavedPhotosAlbum:cgImg
metadata:[saveToSave properties]
completionBlock:^(NSURL *assetURL, NSError *error) {
CGImageRelease(cgImg);
}];