如何在 C# WinRT/winmd 中调整图像大小? [英] How to resize Image in C# WinRT/winmd?

问题描述

我有一个简单的问题，但到目前为止我还没有找到答案:如何在 C# WinRT/WinMD 项目中调整 jpeg 图像的大小并将其另存为新的 jpeg?

I've got simple question, but so far I've found no answer: how to resize jpeg image in C# WinRT/WinMD project and save it as new jpeg?

我正在开发 Windows 8 Metro 应用程序，用于从某个站点下载每日图像并将其显示在动态磁贴上.问题是图像必须小于 1024x1024 且小于 200kB，否则它不会显示在图块上:http://msdn.microsoft.com/en-us/library/windows/apps/hh465403.aspx

I'm developing Windows 8 Metro application for downloading daily image form certain site and displaying it on a Live Tile. The problem is the image must be smaller than 1024x1024 and smaller than 200kB, otherwise it won't show on the tile: http://msdn.microsoft.com/en-us/library/windows/apps/hh465403.aspx

如果我有更大的图像，如何调整它的大小以适合动态磁贴?我正在考虑简单的调整大小，如宽度/2 和高度/2，同时保持纵横比.

If I got larger image, how to resize it to be fit for the Live Tile? I'm thinking just about simple resize like width/2 and height/2 with keeping the aspect ration.

这里的具体要求是代码必须作为 Windows 运行时组件运行，因此 WriteableBitmapEx 库在这里不起作用 - 它仅适用于常规 WinRT 项目.甚至还有一个将 WriteableBitmapEx 作为 winmd 项目的分支，但还远远没有准备好.

The specific requirement here is that the code must run as Windows Runtime Component, so WriteableBitmapEx library won't work here - it's only available for regular WinRT projects. There is even a branch for WriteableBitmapEx as winmd project, but it's far from ready.

推荐答案

如何缩放和裁剪的示例取自 这里:

Example of how to scale and crop taken from here:

async private void BitmapTransformTest()
{
    // hard coded image location
    string filePath = "C:\Users\Public\Pictures\Sample Pictures\fantasy-dragons-wallpaper.jpg";

    StorageFile file = await StorageFile.GetFileFromPathAsync(filePath);
    if (file == null)
        return;

    // create a stream from the file and decode the image
    var fileStream = await file.OpenAsync(Windows.Storage.FileAccessMode.Read);
    BitmapDecoder decoder = await BitmapDecoder.CreateAsync(fileStream);


    // create a new stream and encoder for the new image
    InMemoryRandomAccessStream ras = new InMemoryRandomAccessStream();
    BitmapEncoder enc = await BitmapEncoder.CreateForTranscodingAsync(ras, decoder);

    // convert the entire bitmap to a 100px by 100px bitmap
    enc.BitmapTransform.ScaledHeight = 100;
    enc.BitmapTransform.ScaledWidth = 100;


    BitmapBounds bounds = new BitmapBounds();
    bounds.Height = 50;
    bounds.Width = 50;
    bounds.X = 50;
    bounds.Y = 50;
    enc.BitmapTransform.Bounds = bounds;

    // write out to the stream
    try
    {
        await enc.FlushAsync();
    }
    catch (Exception ex)
    {
        string s = ex.ToString();
    }

    // render the stream to the screen
    BitmapImage bImg = new BitmapImage();
    bImg.SetSource(ras);
    img.Source = bImg; // image element in xaml

}

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