iOS 保存图片到自定义相册

iOS 10开始，保存图片要获得隐私权限，要在info.plist添加一项key是Privacy - Photo Library Usage Description 要不然会报错

保存按钮点击事件

- (void)save {
    PHAuthorizationStatus oldStatus = [PHPhotoLibrary authorizationStatus];

    // 请求\检查访问权限 :
    // 如果用户还没有做出选择，会自动弹框，用户对弹框做出选择后，才会调用block
    // 如果之前已经做过选择，会直接执行block
    [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
        dispatch_async(dispatch_get_main_queue(), ^{
            if (status == PHAuthorizationStatusDenied) { // 用户拒绝当前App访问相册
                if (oldStatus != PHAuthorizationStatusNotDetermined) {
                    DLog(@"提醒用户打开开关");
                }
            } else if (status == PHAuthorizationStatusAuthorized) { // 用户允许当前App访问相册
                [self saveImageIntoAlbum];
            } else if (status == PHAuthorizationStatusRestricted) { // 无法访问相册
                [SVProgressHUD showErrorWithStatus:@"因系统原因，无法访问相册！"];
            }
        });
    }];
}

#pragma mark - 保存图片到自定义相册
- (void)saveImageIntoAlbum
{
    // 获得相片
    PHFetchResult *createdAssets = self.createdAssets;
    if (createdAssets == nil) {
        [SVProgressHUD showErrorWithStatus:@"保存图片失败！"];
        return;
    }

    // 获得相册
    PHAssetCollection *createdCollection = self.createdCollection;
    if (createdCollection == nil) {
        [SVProgressHUD showErrorWithStatus:@"创建或者获取相册失败！"];
        return;
    }

    // 添加刚才保存的图片到【自定义相册】
    NSError *error = nil;
    [[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{
        PHAssetCollectionChangeRequest *request = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:createdCollection];
        [request insertAssets:createdAssets atIndexes:[NSIndexSet indexSetWithIndex:0]];
    } error:&error];

    // 最后的判断
    if (error) {
        [SVProgressHUD showErrorWithStatus:@"保存图片失败！"];
    } else {
        [SVProgressHUD showSuccessWithStatus:@"保存图片成功！"];
    }
}
#pragma mark - 获得当前App对应的自定义相册
- (PHAssetCollection *)createdCollection
{
    // 获得APP名字
    NSString *title = [NSBundle mainBundle].infoDictionary[(__bridge NSString *)kCFBundleNameKey];

    // 抓取所有的自定义相册
    PHFetchResult *collections = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];

    // 查找当前App对应的自定义相册
    for (PHAssetCollection *collection in collections) {
        if ([collection.localizedTitle isEqualToString:title]) {
            return collection;
        }
    }

    /** 当前App对应的自定义相册没有被创建过 **/
    // 创建一个【自定义相册】
    NSError *error = nil;
    __block NSString *createdCollectionID = nil;
    [[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{
        createdCollectionID = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:title].placeholderForCreatedAssetCollection.localIdentifier;
    } error:&error];

    if (error) return nil;

    // 根据唯一标识获得刚才创建的相册
    return [PHAssetCollection fetchAssetCollectionsWithLocalIdentifiers:@[createdCollectionID] options:nil].firstObject;
}
#pragma mark - 获得相片
- (PHFetchResult *)createdAssets
{
    NSError *error = nil;
    __block NSString *assetID = nil;

    // 保存图片到【相机胶卷】
    [[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{
        assetID = [PHAssetChangeRequest creationRequestForAssetFromImage:self.imageView.image].placeholderForCreatedAsset.localIdentifier;
    } error:&error];

    if (error) return nil;

    // 获取刚才保存的相片
    return [PHAsset fetchAssetsWithLocalIdentifiers:@[assetID] options:nil];
}

如果只是保存到系统相册

C语言函数  UIImageWriteToSavedPhotosAlbum 一个函数搞定

注意：
// Adds a photo to the saved photos album.  The optional completionSelector should have the form:
意思就是要实现下面格式的方法，要不然会报错
//  - (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo;