保存图片到【相机胶卷】和【自定义相册】

一、保存图片到【相机胶卷】

方法一：C语言函数

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    UIImageWriteToSavedPhotosAlbum(self.img, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
}


- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
    if (error) {
        NSLog(@"保存失败");
    } else {
        NSLog(@"保存成功");
    }
}

方法二：AssetsLibrary 框架

作为一套老框架，AssetsLibrary 不但有坑，而且还不少。比如，AssetsLibrary 实例需要强引用，遵循写入优先原则…现在已经被 Photos 框架代替，这里就不做介绍。

方法三：Photos 框架 —— #import <Photos/Photos.h>

// 异步执行修改操作

// 在这里保存图片到相册
[[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{  

    [PHAssetChangeRequest creationRequestForAssetFromImage:self.img];

} completionHandler:^(BOOL success, NSError * _Nullable error) {

    if (error) {
        NSLog(@"保存失败");
    } else {
        NSLog(@"保存成功");
    }
}];

// 同步执行修改操作

NSError *error = nil;

[[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{

    [PHAssetChangeRequest creationRequestForAssetFromImage:self.img];

} error:&error];

if (error) {
    NSLog(@"保存失败");
} else {
    NSLog(@"保存成功");
}

二、保存图片到【自定义相册】

Photos 框架基本方法概况

• PHAsset：一个 PHAsset 对象就代表相册中的一张图片或者视频

  • 查：[PHAsset fetchAssets…]

  • 增删改：[PHAssetChangeRequest creation…/delete…]

• PHAssetCollection：一个 PHAssetCollection 代表一个相册

  • 查：[PHAssetCollection fetchAssetCollections…]

  • 增删改：[PHAssetCollectionChangeRequest creation…/delete…]

方法步骤

• 0.判断相册权限

PHAuthorizationStatus oldStatus = [PHPhotoLibrary authorizationStatus];

// 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) {
    // block中是在子线程中进行,如果刷新UI需要回到主线程
    dispatch_async(dispatch_get_main_queue(), ^{
        if (status == PHAuthorizationStatusDenied) {
            NSLog(@"用户拒绝当前APP访问相册");

            // 如果状态不等于没有做决定
            if (oldStatus != PHAuthorizationStatusNotDetermined) {
                NSLog(@"提醒用户打开开关");
            }
        } else if (status == PHAuthorizationStatusAuthorized) {
            NSLog(@"用户允许当前APP访问相册");
        } else if (status == PHAuthorizationStatusRestricted) {
            NSLog(@"无法访问相册");
        }
    });
}];

• 1.保存图片到【相机胶卷】

NSError *error = nil;

__block NSString *assetID = nil;  // 图片的ID
[[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{
    assetID = [PHAssetChangeRequest creationRequestForAssetFromImage:image].placeholderForCreatedAsset.localIdentifier;
} error:&error];
if (error) {
    NSLog(@"MYPhotoTool - 保存失败");
}

• 2.拥有一个【自定义相册】

// 获取软件名字
NSString *title = [NSBundle mainBundle].infoDictionary[(NSString *)kCFBundleNameKey];

// 获取所有自定义相册
PHFetchResult<PHAssetCollection *> *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) {

    // *** 如果存在自定义相册
    if ([collection.localizedTitle isEqualToString:collectionName]) {
        return collection;
    }
}

// *** 自定义相册没有被创建过

__block NSString *ID = nil;

NSError *error = nil;
[[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{

    // 创建一个【自定义相册】
    PHAssetCollectionChangeRequest *request = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:collectionName];
    // 获取站位标识
    ID = request.placeholderForCreatedAssetCollection.localIdentifier;
} error:&error];

if (error) {
    NSLog(@"MYPhotoTool - 创建自定义相册失败");
    return nil;
}

// 根据站位标识获取当前APP对应的自定义相册
PHAssetCollection *collection = [PHAssetCollection fetchAssetCollectionsWithLocalIdentifiers:@[ID] options:nil].firstObject;

• 3.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:collection];
    id<NSFastEnumeration> assetIDs = [PHAsset fetchAssetsWithLocalIdentifiers:@[assetID] options:nil];
    [request insertAssets:assetIDs atIndexes:[NSIndexSet indexSetWithIndex:0]];
} error:&error];

if (error) {
    NSLog(@"MYPhotoTool - 保存失败");
}

三、选择照片到项目中

1.从相册中选择照片

• UIImagePickerController（自带选择界面）（只能选择单张图片）

UIImagePickerController *picker = [[UIImagePickerController alloc] init];
picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
picker.delegate = self;  // <UINavigationControllerDelegate, UIImagePickerControllerDelegate>
[self presentViewController:picker animated:YES completion:nil];

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info
{
    [picker dismissViewControllerAnimated:YES completion:nil];    
    self.imgView.image = info[UIImagePickerControllerOriginalImage];
}

• AssetsLibrary 框架

• Photos 框架

网上基于 Photos 框架的三方框架一搜一大堆，就不浪费时间造轮子了。其实是最近项目太紧了，没时间弄，等年后抽时间把这部分补充一下吧。

2.选择相机拍摄的照片

• UIImagePickerController（自带选择界面）

  和从相册中选择照片一样，改变 sourceType 就可以了

• AVCaptureSession —— #import <AVFoundation/AVFoundation.h>

保存图片到【相机胶卷】和【自定义相册】框架和 DEMO 已经上传到 github ，下载地址：MYPhotoTool