问题描述

我使用了

我可能想要返回原始 BitmapImage 的副本，而不是修改原始文件.

没有直接复制一个BitmapImage的好方法，但是我们可以多次重复StorageFile.

如果您只想选择一张图片，显示它，同时显示原始图片的调整大小的图片，您可以将 StorageFile 作为参数传递，如下所示:

public static async TaskResizedImage(StorageFile ImageFile, int maxWidth, int maxHeight){IRandomAccessStream 输入流 = 等待 ImageFile.OpenReadAsync();BitmapImage sourceImage = new BitmapImage();sourceImage.SetSource(输入流);var origHeight = sourceImage.PixelHeight;var origWidth = sourceImage.PixelWidth;var ratioX = maxWidth/(float)origWidth;var ratioY = maxHeight/(float)origHeight;var ratio = Math.Min(ratioX, ratioY);var newHeight = (int)(origHeight * ratio);var newWidth = (int)(origWidth * ratio);sourceImage.DecodePixelWidth = newWidth;sourceImage.DecodePixelHeight = newHeight;返回源图像；}

在这种情况下，您只需要调用此任务并显示调整大小的图像，如下所示:

smallImage.Source = await ResizedImage(file, 250, 250);

如果你想保留 BitmapImage 参数由于某些原因(比如 sourceImage 可能是修改过的位图但不是直接从文件中加载的)，并且你想重新调整这个新图片的大小另一个，您需要先将调整大小的图片另存为文件，然后打开此文件并重新调整大小.

I have used the code from http://www.codeproject.com/Tips/552141/Csharp-Image-resize-convert-and-save to resize images programmatically. However, that project uses the System.Drawing libraries, which are not available to Windows 10 applications.

I have tried using the BitmapImage class from Windows.UI.Xaml.Media.Imaging instead, but it does not seem to offer the functionality that was found in System.Drawing..

Has anyone had any luck being able to resize (scale down) images in Windows 10? My application will be processing images from multiple sources, in different formats/sizes, and I am trying to resize the actual images to save space, rather than just letting the application size it to fit the Image in which it is being displayed.

EDIT

I have modified the code from the above mentioned link, and have a hack which works for my specific need. Here it is:

public static BitmapImage ResizedImage(BitmapImage sourceImage, int maxWidth, int maxHeight)
{
    var origHeight = sourceImage.PixelHeight;
    var origWidth = sourceImage.PixelWidth;
    var ratioX = maxWidth/(float) origWidth;
    var ratioY = maxHeight/(float) origHeight;
    var ratio = Math.Min(ratioX, ratioY);
    var newHeight = (int) (origHeight * ratio);
    var newWidth = (int) (origWidth * ratio);

    sourceImage.DecodePixelWidth = newWidth;
    sourceImage.DecodePixelHeight = newHeight;

    return sourceImage;
}

This way seems to work, but ideally rather than modifying the original BitmapImage, I would like to create a new/copy of it to modify and return instead.

Here is a shot of it in action:

I may want to return a copy of the original BitmapImage rather than modifying the original.

There is no good method to directly copy a BitmapImage, but we can reuse StorageFile for several times.

If you just want to select a picture, show it and in the meanwhile show the re-sized picture of original one, you can pass the StorageFile as parameter like this:

public static async Task<BitmapImage> ResizedImage(StorageFile ImageFile, int maxWidth, int maxHeight)
{
    IRandomAccessStream inputstream = await ImageFile.OpenReadAsync();
    BitmapImage sourceImage = new BitmapImage();
    sourceImage.SetSource(inputstream);
    var origHeight = sourceImage.PixelHeight;
    var origWidth = sourceImage.PixelWidth;
    var ratioX = maxWidth / (float)origWidth;
    var ratioY = maxHeight / (float)origHeight;
    var ratio = Math.Min(ratioX, ratioY);
    var newHeight = (int)(origHeight * ratio);
    var newWidth = (int)(origWidth * ratio);

    sourceImage.DecodePixelWidth = newWidth;
    sourceImage.DecodePixelHeight = newHeight;

    return sourceImage;
}

In this scenario you just need to call this task and show the re-sized image like this:

smallImage.Source = await ResizedImage(file, 250, 250);

If you want to keep the BitmapImage parameter due to some reasons (like the sourceImage might be a modified bitmap but not directly loaded from file), and you want to re-size this new picture to another one, you will need to save the re-sized picture as a file at first, then open this file and re-size it again.

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