前言

在用Swift寫項目時，發(fā)現(xiàn)Kingfisher中可以對網(wǎng)絡(luò)圖片進行縮放并添加圓角等功能，感覺這個功能很實用。終于SDWebImage 5.0也有了這個功能。今天來講一下SDWebImage的常用功能。

SDWebImage使用

先來看下面兩個方法，你會發(fā)下下面這個方法中多了一個SDWebImageContext類型的參數(shù)。實現(xiàn)縮放和添加圓角等功能主要就是在這個參數(shù)上。

///以前常用方法
- (void)sd_setImageWithURL:(nullable NSURL *)url
          placeholderImage:(nullable UIImage *)placeholder
                   options:(SDWebImageOptions)options
///添加圓角功能使用方法
- (void)sd_setImageWithURL:(nullable NSURL *)url
          placeholderImage:(nullable UIImage *)placeholder
                   options:(SDWebImageOptions)options
                   context:(nullable SDWebImageContext *)context

SDWebImageContext這個進去你會發(fā)現(xiàn)這個其實是一個NSDictionary<SDWebImageContextOption, id>類型。
SDWebImageContextOption中有一個SDWebImageContextImageTransformer為key的值。這個key對應(yīng)的值必須是id<SDImageTransformer>的對象。
SDWebImage中給我們提供了幾個這種類

SDImagePipelineTransformer       //它可以將多個變換器綁定在一起，讓圖像按順序逐個變換并生成最終圖像
SDImageRoundCornerTransformer //圓角
SDImageResizingTransformer //調(diào)整大小
SDImageCroppingTransformer //裁剪
SDImageFlippingTransformer //翻轉(zhuǎn)
SDImageRotationTransformer //旋轉(zhuǎn)
SDImageTintTransformer //Tint顏色
SDImageBlurTransformer //毛玻璃效果
SDImageFilterTransformer //濾鏡

需要實現(xiàn)調(diào)整大小并設(shè)置圓角的代碼如下

    /// 圓角，這里的Radius和Size都是已像素為單位的，可以獲取手機的Scale計算出具體大小
    SDImageRoundCornerTransformer *transformer1 = [SDImageRoundCornerTransformer transformerWithRadius:100 corners:UIRectCornerAllCorners borderWidth:0 borderColor:nil];
    /// 大小
    SDImageResizingTransformer *transformer2 = [SDImageResizingTransformer transformerWithSize:CGSizeMake(200, 200) scaleMode:(SDImageScaleModeAspectFill)];
    
    SDImagePipelineTransformer *transformer = [SDImagePipelineTransformer transformerWithTransformers:@[transformer1, transformer2]];
    
    [self.roundIV sd_setImageWithURL:url placeholderImage:nil options:SDWebImageRetryFailed context:@{ SDWebImageContextImageTransformer : transformer}];

另外SDWebImageOptions這個枚舉有新增，有一個值我們可以用到SDWebImageAvoidDecodeImage防止解碼圖片。之前版本中防止加載高清大圖導(dǎo)致內(nèi)存暴漲一般采取的措施是如下設(shè)置（需要來回設(shè)置）?，F(xiàn)在只需通過SDWebImageAvoidDecodeImage就可以了，方便很多。

[[SDImageCache sharedImageCache] setShouldDecompressImages:NO];
[[SDWebImageDownloader sharedDownloader] setShouldDecompressImages:NO];

SDWebImageDownloaderConfig下載配置

/// 用戶名
[SDWebImageDownloader sharedDownloader].config.username = @"httpwatch";
/// 密碼
[SDWebImageDownloader sharedDownloader].config.password = @"httpwatch01";
[[SDWebImageDownloader sharedDownloader] setValue:@"SDWebImage Demo" forHTTPHeaderField:@"AppName"];

/// 默認6個
[SDWebImageDownloader sharedDownloader].config.maxConcurrentDownloads = 6;
/// 默認15秒
[SDWebImageDownloader sharedDownloader].config.downloadTimeout = 15;

SDAnimatedImageView 加載動圖

SDWebImageCacheKeyFilter 緩存路徑過濾

有些圖片后臺返回的URL每次都不一樣（如后面的參數(shù)不同），可以根據(jù)需求將該圖片的存儲路徑進行過濾一下，可以不用每次都去下載

    SDWebImageCacheKeyFilter *filter = [SDWebImageCacheKeyFilter cacheKeyFilterWithBlock:^NSString * _Nullable(NSURL * _Nonnull url) {
        if (![url.absoluteString hasPrefix:@"https://ss0.bdstatic.com"]) {
            return url.absoluteString;
        }
//        NSURLComponents *otherUrl = [[NSURLComponents alloc] init];
//        otherUrl.scheme = url.scheme;
//        otherUrl.host = url.host;
//        otherUrl.path = url.path;
        return @"https://ss0.bdstatic.com";
    }];

    [SDWebImageManager sharedManager].cacheKeyFilter = filter;

    ///正確路徑
    NSString *urlString = @"https://ss0.bdstatic.com/70cFvHSh_Q1YnxGkpoWK1HF6hhy/it/u=1307986195,877877609&fm=15&gp=0.jpg";
    NSURL *url = [NSURL URLWithString:urlString];
    
    [self.roundIV sd_setImageWithURL:url completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
        NSLog(@"%f", image.size.width);
    }];
    
    ///不正確路徑，但匹配緩存路徑
    NSString *urlString1 = @"https://ss0.bdstatic.com/70cFvHSh_Q1YnxGkpoWK1HF6hhy.jpg";

    NSURL *url1 = [NSURL URLWithString:urlString1];
    [self.normalIV sd_setImageWithURL:url1 completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
        NSLog(@"%f", image.size.width);
    }];

SDImageCache 緩存

/// 緩存圖片
- (void)storeImage:(nullable UIImage *)image
         imageData:(nullable NSData *)imageData
            forKey:(nullable NSString *)key
            toDisk:(BOOL)toDisk
        completion:(nullable SDWebImageNoParamsBlock)completionBlock

/// 同步清理
- (void)clearMemory;

///異步清理
- (void)clearDiskOnCompletion:(nullable SDWebImageNoParamsBlock)completion;
/// 同步統(tǒng)計
- (NSUInteger)totalDiskSize;

/// 異步統(tǒng)計
- (void)calculateSizeWithCompletionBlock:(nullable SDImageCacheCalculateSizeBlock)completionBlock;