WPF图像缓存 [英] WPF Image Caching

问题描述

我有一个WPF应用程序，它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，然后将其渲染为< image> 元素。

<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 - 然后应该在< image> 元素中显示。

使用 Image.Source = null; ，我可以清除图像文件< image> 元素，因此它会显示一个空格。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< image> 元素中，则仍会显示旧图像。

我使用以下逻辑：

  //在此覆盖临时文件文件
 
 //清除对临时图像的引用
 Image_Preview.Source = null; 
 
 //加载新图像（相同的源文件名）
 Image = new BitmapImage（）; 
 Image.BeginInit（）; 
 Image.CacheOption = BitmapCacheOption.OnLoad; 
 Image.UriSource = new Uri（file）; 
 Image.EndInit（）; 
 Image_Preview.Source = Image; 
  

< image> 元素不会更改，即使原始文件已被完全替换。这里是否存在我不知道的图像缓存问题？

解决方案

默认情况下，WPF缓存从URI加载的BitmapImages 。

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

  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; 
  

或者你直接从Stream加载BitmapImage：

  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; 
  

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.

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.

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.

I am using the following logic:

// 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;

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?

解决方案

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

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;

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;

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