起源：前兩天有人說(shuō)使用SDWebImage下載圖片后保存到相冊(cè)發(fā)現(xiàn)圖片被壓縮了察藐，原圖2.2M歪脏，保存到相冊(cè)后傳到Mac上顯示圖片大小只有500K左右。于是嘗試了一下般堆，代碼如下：

    NSURL *imgUrl = [NSURL URLWithString:@"https://xxxx.png"];

    [[SDWebImageDownloader sharedDownloader] downloadImageWithURL:imgUrl completed:^(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, BOOL finished) {
        if (image) {
            UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
            //清除sd緩存在孝，防止圖片被sdwebimage緩存
//            [[SDImageCache sharedImageCache] clearDiskOnCompletion:nil];
//            [[SDImageCache sharedImageCache] clearMemory];
        }
    }];

然后到相冊(cè)里一查還真是變成了500多k、首先查看data.length淮摔，大小和原圖一致，確定了不是SDWebImage 框架的問(wèn)題始赎。那么一定是這個(gè)函數(shù)對(duì)圖片進(jìn)行了壓縮：

// Adds a photo to the saved photos album.  The optional completionSelector should have the form:
//  - (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo;
UIKIT_EXTERN void UIImageWriteToSavedPhotosAlbum(UIImage *image, __nullable id completionTarget, __nullable SEL completionSelector, void * __nullable contextInfo) __TVOS_PROHIBITED;

于是乎使用Photos框架中的PHPhotoLibrary來(lái)存儲(chǔ)圖片以解決這個(gè)問(wèn)題和橙，代碼如下：

[[SDWebImageDownloader sharedDownloader] downloadImageWithURL:imgUrl completed:^(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, BOOL finished)  {
        
        NSLog(@"dataLen:%lu",data.length);
        if (finished)
        {
            UIImage * imgsave = image;
            NSString * path = NSHomeDirectory();
            //圖片存儲(chǔ)的沙盒路徑
            NSString * Pathimg = [path stringByAppendingString:@"/Documents/test.png"];
            [UIImagePNGRepresentation(imgsave) writeToFile:Pathimg atomically:YES];
            
            //使用url存儲(chǔ)到相冊(cè)
            NSURL *imagePathUrl = [NSURL fileURLWithPath:Pathimg];
            [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
                if (status == PHAuthorizationStatusAuthorized) {//權(quán)限判斷
                    PHPhotoLibrary *library = [PHPhotoLibrary sharedPhotoLibrary];
                    [library performChanges:^{
                        [PHAssetChangeRequest creationRequestForAssetFromImageAtFileURL:imagePathUrl];
                    } completionHandler:^(BOOL success, NSError * _Nullable error) {
                        if (success) NSLog(@"保存成功");
                        else NSLog(@"保存失敗");
                    }];
                }
            }];
        }
    }];