window8 如何较简单实现图片剪切和缩放？

Question

从系统导入图片，然后生成固定定大小比如400*400的图片：如果导入的图片太大进行压缩处理，如果图片太小用黑色填充补充

Answer 1

自己使用photoshop或者Office Photo viewer编辑吧。。。

Answer 2

你可以做一个自定义控件，如下是一个简单的思路，你可以自己完善剩余的代码。

Xaml：

<Grid Background="Black">
        <Image VerticalAlignment="Center" HorizontalAlignment="Center" ImageOpened="Image_ImageOpened_1"/>
</Grid>

在Code behind代码中：

private async void Image_ImageOpened_1(object sender, RoutedEventArgs e)
        {
 var image = sender as Image;
                var source = image.GetValue(Image.SourceProperty) as Windows.UI.Xaml.Media.Imaging.BitmapImage;

                #region change the image stretch
                if (source.PixelHeight < this.ActualHeight && source.PixelWidth < this.ActualWidth)
                    image.Stretch = Stretch.None;
                else
                    image.Stretch = Stretch.Uniform;
                #endregion
        }

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Thanks! Damon.Tian

Answer 3

你可以做一个自定义控件，如下是一个简单的思路，你可以自己完善剩余的代码。

Xaml：

<Grid Background="Black">
        <Image VerticalAlignment="Center" HorizontalAlignment="Center" ImageOpened="Image_ImageOpened_1"/>
</Grid>

在Code behind代码中：

private async void Image_ImageOpened_1(object sender, RoutedEventArgs e)
        {
 var image = sender as Image;
                var source = image.GetValue(Image.SourceProperty) as Windows.UI.Xaml.Media.Imaging.BitmapImage;

                #region change the image stretch
                if (source.PixelHeight < this.ActualHeight && source.PixelWidth < this.ActualWidth)
                    image.Stretch = Stretch.None;
                else
                    image.Stretch = Stretch.Uniform;
                #endregion
        }

---

Thanks! Damon.Tian

先谢谢了 不过我的 需求没那么简单 需要要代码来剪切和压缩图片，不是调简单的控件属性。。。

Answer 4

把你的图片流初始化一个位图解码器类，然后对位图进行转换（压缩等）

                    BitmapDecoder decoder = await BitmapDecoder.CreateAsync(fileStream);

                    BitmapTransform transform = new BitmapTransform() {
                        ScaledWidth = Convert.ToUInt32(Scenario4WriteableBitmap.PixelWidth),
                        ScaledHeight = Convert.ToUInt32(Scenario4WriteableBitmap.PixelHeight)};
                   
                    PixelDataProvider pixelData = await decoder.GetPixelDataAsync(
                        BitmapPixelFormat.Bgra8,    
                        BitmapAlphaMode.Straight,
                        transform,
                        ExifOrientationMode.IgnoreExifOrientation, 
                        ColorManagementMode.DoNotColorManage);

                    byte[] sourcePixels = pixelData.DetachPixelData();

                    using (Stream stream = WriteableBitmap.PixelBuffer.AsStream())
                    {
                        await stream.WriteAsync(sourcePixels, 0, sourcePixels.Length);
                    }

Answer 5

把你的图片流初始化一个位图解码器类，然后对位图进行转换（压缩等）

                    BitmapDecoder decoder = await BitmapDecoder.CreateAsync(fileStream);

                    BitmapTransform transform = new BitmapTransform() {
                        ScaledWidth = Convert.ToUInt32(Scenario4WriteableBitmap.PixelWidth),
                        ScaledHeight = Convert.ToUInt32(Scenario4WriteableBitmap.PixelHeight)};
                   
                    PixelDataProvider pixelData = await decoder.GetPixelDataAsync(
                        BitmapPixelFormat.Bgra8,    
                        BitmapAlphaMode.Straight,
                        transform,
                        ExifOrientationMode.IgnoreExifOrientation, 
                        ColorManagementMode.DoNotColorManage);

                    byte[] sourcePixels = pixelData.DetachPixelData();

                    using (Stream stream = WriteableBitmap.PixelBuffer.AsStream())
                    {
                        await stream.WriteAsync(sourcePixels, 0, sourcePixels.Length);
                    }

这个如果图片太小，没法办法填充黑色吧！！！

Answer 6

小图剪切后要实现这种效果

Answer 7

Hi,

那可以使用WriteableBitmap来做。可以通过PixelBuffer直接对像素进行操作，不过WinRT里WriteableBitmap大幅简化过，你可以试试使用第三方工具WriteableBitmapEx来做。

WriteableBitmapEx：

http://writeablebitmapex.codeplex.com/

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Aaron Xue [MSFT]
MSDN Community Support | Feedback to us
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