UIImage 与 NSData - 图像压缩依赖

Question

我了解在连接到 3G 网络时下载图像时需要压缩图像，但我的图像看起来非常糟糕...我正在缓存下载的图像，我意识到图像的质量取决于活动联系。我的代码：

        KTMember *member = [[DataManager sharedManager] getMemberWithId:memberId];
    if (member) {
        NSLog(@"caching member %d locally",member.memberId);
        memberImg = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:member.imageUrl]]];
        [[DataManager sharedManager] saveImageToDocuments:memberImg withId:memberId];
        return memberImg;
    } else {
        return nil;
    }

所以问题是 - 即使活动网络是 3G，是否有任何方法可以覆盖图像压缩？

谢谢

Answer 1

没有针对慢速连接自适应地增加图像压缩的全局机制。您所描述的内容需要服务器上的自定义代码，并且会因服务器而异。

提供这些图片的服务是什么？

Answer 2

编辑：感谢您修复我的答案，Verizon 网络优化有一些图像压缩机制。

我认为，图像的质量，就字节流而言，取决于服务器是否提供压缩。

但是有一些解决方案。您还可以使用线程编程实现NSURLConnectionDataDelegate 来处理来自 URL 请求的数据。有一个有趣的方法：

/** connection:didReceiveResponse: is called when
 *               enough data has been read to construct an
 *               NSURLResponse object. In the event of a protocol
 *               which may return multiple responses (such as HTTP
 *               multipart/x-mixed-replace) the delegate should be
 *               prepared to inspect the new response and make
 *               itself ready for data callbacks as appropriate.
 **/

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;

/** connection:didReceiveData: is called with a single
  *              immutable NSData object to the delegate,
  *              representing the next portion of the data loaded
  *              from the connection.  This is the only guaranteed
  *              for the delegate to receive the data from the
  *              resource load
  **/

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;

/** connection:willCacheResponse: gives the delegate
  *              an opportunity to inspect and modify the
  *              NSCachedURLResponse which will be cached by the
  *              loader if caching is enabled for the original
  *              NSURLRequest.  Returning nil from this delegate
  *              will prevent the resource from being cached.  Note
  *              that the -data method of the cached response may
  *              return an autoreleased in-memory copy of the true
  *              data, and should not be used as an alternative to
  *              receiving and accumulating the data through
  *              connection:didReceiveData
  **/

- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse;

/** connectionDidFinishLoading: is called when all
  *              connection processing has completed successfully,
  *              before the delegate is released by the
  *              connection
  **/

- (void)connectionDidFinishLoading:(NSURLConnection *)connection;

您还可以在didReceiveData 中管理您的数据，累积每个传入的数据，当完成下载时，在connectionDidFinishLoading 中，您可以处理您收到的所有图像的NSData。

希望对你有帮助。