下载时如何在 UIImageView 中显示渐进式 JPEG? [英] How do I display a progressive JPEG in an UIImageView while it is being downloaded?

问题描述

从网上下载图像并在 UIImageView 中显示它是相当容易的.但是，这要求图像在显示给用户之前完全下载，完全打败了渐进式 JPEG(和 PNG)图像.

Downloading an image from the net and showing it in an UIImageView is fairly easy. However, this requires the image to be completely downloaded before it is shown to the user, completely defeating progressive JPEG (and PNG) images.

如何在传输完成时渲染部分下载的图像?我会想象 SDK 有一些可以更新图像的回调函数，但我找不到这样的函数.使用当前的 iOS SDK 是否有可能?

How can I render the partially downloaded images while the transfer is being done? I would imagine the SDK to have some callback function which would update the image, but I can't find such a function. Is it possible at all with the current iOS SDK?

推荐答案

您是否尝试在调用 didReceiveData 时部分渲染 UIImage ...?有点像……

Did you try to render the UIImage partially as didReceiveData gets called … ? Something like …

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    //TODO: add some error handling in case the image could not be created
    UIImage *img=[UIImage imageWithData:data];
    if (img) {
        self.imageView.image=img;
    }
}

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