一.獲取單張圖片

思路:

• 1.利用UIImagePickerController可以從系統(tǒng)自帶的App(照片\相機(jī))中獲得圖片
• 2.設(shè)置代理,遵守代理協(xié)議
• 注意這個(gè)UIImagePickerController類比較特殊,需要遵守兩個(gè)代理協(xié)議

@interface ViewController () <UIImagePickerControllerDelegate, UINavigationControllerDelegate>

• 3.實(shí)現(xiàn)代理的方法didFinishPickingMediaWithInfo

- (void)getImageFromIpc
{
    // 1.判斷相冊是否可以打開
    if (![UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]) return;
    // 2. 創(chuàng)建圖片選擇控制器
    UIImagePickerController *ipc = [[UIImagePickerController alloc] init];
    /**
     typedef NS_ENUM(NSInteger, UIImagePickerControllerSourceType) {
     UIImagePickerControllerSourceTypePhotoLibrary, // 相冊
     UIImagePickerControllerSourceTypeCamera, // 用相機(jī)拍攝獲取
     UIImagePickerControllerSourceTypeSavedPhotosAlbum // 相簿
     }
     */
    // 3. 設(shè)置打開照片相冊類型(顯示所有相簿)  
    ipc.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    // ipc.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
    // 照相機(jī)
    // ipc.sourceType = UIImagePickerControllerSourceTypeCamera;
    // 4.設(shè)置代理
    ipc.delegate = self;
    // 5.modal出這個(gè)控制器
    [self presentViewController:ipc animated:YES completion:nil];
}

#pragma mark -- <UIImagePickerControllerDelegate>--
// 獲取圖片后的操作
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info
{
    // 銷毀控制器
    [picker dismissViewControllerAnimated:YES completion:nil];

    // 設(shè)置圖片
    self.imageView.image = info[UIImagePickerControllerOriginalImage];
}

二.獲取多張圖片

思路:

• 導(dǎo)入頭文件#import <Photos/Photos.h>
• PHAsset : 一個(gè)資源, 比如一張圖片\一段視頻
• PHAssetCollection : 一個(gè)相簿
• PHImageManager 圖片管理者,是單例,發(fā)送請求才能從asset獲取圖片
• PHImageRequestOptions圖片請求選項(xiàng)
• 注意:這個(gè)類是iOS8開始推廣,iOS9開始廢棄之前的方法
  系統(tǒng)適配iOS8之前,用下面這個(gè)庫里面的API

#import <AssetsLibrary/AssetsLibrary.h>

1.獲得所有相簿的原圖

- (void)getOriginalImages
{
    // 獲得所有的自定義相簿
    PHFetchResult<PHAssetCollection *> *assetCollections = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];
    // 遍歷所有的自定義相簿
    for (PHAssetCollection *assetCollection in assetCollections) {
        [self enumerateAssetsInAssetCollection:assetCollection original:YES];
    }
    
    // 獲得相機(jī)膠卷
    PHAssetCollection *cameraRoll = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeSmartAlbum subtype:PHAssetCollectionSubtypeSmartAlbumUserLibrary options:nil].lastObject;
    // 遍歷相機(jī)膠卷,獲取大圖
    [self enumerateAssetsInAssetCollection:cameraRoll original:YES];
}

2.獲得所有相簿中的縮略圖

- (void)getThumbnailImages
{
    // 獲得所有的自定義相簿
    PHFetchResult<PHAssetCollection *> *assetCollections = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];
    // 遍歷所有的自定義相簿
    for (PHAssetCollection *assetCollection in assetCollections) {
        [self enumerateAssetsInAssetCollection:assetCollection original:NO];
    }
    // 獲得相機(jī)膠卷
    PHAssetCollection *cameraRoll = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeSmartAlbum subtype:PHAssetCollectionSubtypeSmartAlbumUserLibrary options:nil].lastObject;
    [self enumerateAssetsInAssetCollection:cameraRoll original:NO];
}

3.遍歷相冊

/**
 *  遍歷相簿中的所有圖片
 *  @param assetCollection 相簿
 *  @param original        是否要原圖
 */
- (void)enumerateAssetsInAssetCollection:(PHAssetCollection *)assetCollection original:(BOOL)original
{
    NSLog(@"相簿名:%@", assetCollection.localizedTitle);
    
    PHImageRequestOptions *options = [[PHImageRequestOptions alloc] init];
    // 同步獲得圖片, 只會(huì)返回1張圖片
    options.synchronous = YES;

    // 獲得某個(gè)相簿中的所有PHAsset對(duì)象
    PHFetchResult<PHAsset *> *assets = [PHAsset fetchAssetsInAssetCollection:assetCollection options:nil];
    for (PHAsset *asset in assets) {
        // 是否要原圖
        CGSize size = original ? CGSizeMake(asset.pixelWidth, asset.pixelHeight) : CGSizeZero;
        
        // 從asset中獲得圖片
        [[PHImageManager defaultManager] requestImageForAsset:asset targetSize:size contentMode:PHImageContentModeDefault options:options resultHandler:^(UIImage * _Nullable result, NSDictionary * _Nullable info) {
            NSLog(@"%@", result);
        }];
    }
}