WPF 图像缓存 [英] WPF Image Caching

问题描述

我有一个 WPF 应用程序，可以从视频文件中获取快照图像.用户可以定义从中获取图像的时间戳.然后将图像保存到磁盘上的临时位置，然后渲染到 元素中.

I have a WPF application that takes a snapshot image from a video file. The user can define the timestamp from which to take the image. The image is then saved to a temporary location on disk, and is then rendered into an <image> element.

然后用户应该能够选择不同的时间戳，然后覆盖磁盘上的临时文件 - 然后这应该显示在 <image> 元素中.

The user should then be able to select a different timestamp, which then overwrites the temporary file on disk - this should then be displayed within the <image> element.

使用 Image.Source = null;，我可以从 元素清除图像文件，所以它显示一个空格代替.但是，如果源图像文件随后被新图像(具有相同名称)覆盖并加载到 元素中，它仍然显示旧图像.

Using Image.Source = null;, I can clear the image file from the <image> element, so it displays a blank space instead. However, if the source image file is then overwritten with a new image (with the same name) and loaded into the <image> element, it still shows the old image.

我正在使用以下逻辑:

// Overwrite temporary file file here

// Clear out the reference to the temporary image
Image_Preview.Source = null;

// Load in new image (same source file name)
Image = new BitmapImage();
Image.BeginInit();
Image.CacheOption = BitmapCacheOption.OnLoad;
Image.UriSource = new Uri(file);
Image.EndInit();
Image_Preview.Source = Image;

显示在 元素中的图像不会改变，即使原始文件已被完全替换.此处是否存在我不知道的图像缓存问题?

The image displayed in the <image> element does not change, even though the original file has been completely replaced. Is there an image caching issue here that I am not aware of?

推荐答案

默认情况下，WPF 缓存从 URI 加载的 BitmapImages.

By default, WPF caches BitmapImages that are loaded from URIs.

您可以通过设置 BitmapCreateOptions.IgnoreImageCache 标志来避免这种情况:

You can avoid that by setting the BitmapCreateOptions.IgnoreImageCache flag:

var image = new BitmapImage();

image.BeginInit();
image.CreateOptions = BitmapCreateOptions.IgnoreImageCache;
image.CacheOption = BitmapCacheOption.OnLoad;
image.UriSource = new Uri(file);
image.EndInit();

Image_Preview.Source = image;

或者您直接从流加载 BitmapImage:

Or you load the BitmapImage directly from a Stream:

var image = new BitmapImage();

using (var stream = new FileStream(file, FileMode.Open, FileAccess.Read))
{
    image.BeginInit();
    image.CacheOption = BitmapCacheOption.OnLoad;
    image.StreamSource = stream;
    image.EndInit();
}

Image_Preview.Source = image;

这篇关于WPF 图像缓存的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！