StorageItemThumbnail 中的位图在 GridView 中显示错误的尺寸

Question

我目前正在构建一个应用程序，但我似乎无法弄清楚的一个错误是：

这些图像是 PDF 页面快照，实际上是纵向格式。不知何故，它不会正确显示。我实际上可以看到错误的尺寸和它应该显示的尺寸。

有谁知道它为什么会这样做？

转换器代码：

public object Convert(object value, Type targetType, object parameter, string language)
{
    BitmapImage image = null;

    if (value != null)
    {
        if (value.GetType() != typeof(StorageItemThumbnail))
        {
            throw new ArgumentException("Expected a StorageItemThumbnail as binding input.");
        }

        if (targetType != typeof(ImageSource))
        {
            throw new ArgumentException("Expected ImageSource as binding output.");
        }

        if ((StorageItemThumbnail)value == null)
        {
            System.Diagnostics.Debug.WriteLine("Thumbnail is null.");
            return image;
        }

        image = new BitmapImage();
        using (var thumbNailClonedStream = ((StorageItemThumbnail)value).CloneStream())
        {
            image.DecodePixelType = DecodePixelType.Logical;

            _ = image.SetSourceAsync(thumbNailClonedStream);
        }
    }

    return image;
}

缩略图检索（destinationFile = StorageFile）：

StorageItemThumbnail thumbnail = await destinationFile.GetThumbnailAsync(ThumbnailMode.PicturesView, 500, ThumbnailOptions.UseCurrentScale);
CurrentPages.Add(new AppPage
{
    ImageFile = destinationFile,
    OriginalFile = file,
    Thumbnail = thumbnail
});

网格视图XAML:

<GridView Name="pagesViewer" ItemsSource="{x:Bind CurrentPages, Mode=OneWay}" Margin="0,0,0,40" Grid.Row="1" CanDrag="True" CanDragItems="True" CanReorderItems="True" Background="White" AllowDrop="True" Drop="pagesViewer_Drop" DragOver="pagesViewer_DragOver">
    <GridView.ItemTemplate>
        <DataTemplate x:DataType="local:AppPage">
            <StackPanel Height="280" Width="200" Margin="12" AutomationProperties.Name="{x:Bind PageNumber}" ToolTipService.ToolTip="{x:Bind OriginalFile.Name}" Background="WhiteSmoke" IsRightTapEnabled="True">
                <StackPanel.ContextFlyout>
                    <MenuFlyout>
                        <MenuFlyout.Items>
                            <MenuFlyoutItem x:Name="DeletePage" Text="Remove Page" />
                            <MenuFlyoutItem x:Name="AddBlankBefore" Text="Add Blank Before" />
                            <MenuFlyoutItem x:Name="AddBlankAfter" Text="Add Blank After" />
                        </MenuFlyout.Items>
                    </MenuFlyout>
                </StackPanel.ContextFlyout>
                <Image Source="{x:Bind Thumbnail, Converter={StaticResource ResourceKey=ThumbnailConverter}}" Height="240" Width="200" Stretch="Uniform" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" />
                <StackPanel Margin="0,12">
                    <TextBlock Text="{x:Bind PageNumber, Mode=OneWay}" Foreground="Black" FontWeight="Light" FontSize="15" TextAlignment="Center" />
                </StackPanel>
            </StackPanel>
        </DataTemplate>
    </GridView.ItemTemplate>
    <GridView.ItemsPanel>
        <ItemsPanelTemplate>
            <ItemsWrapGrid MaximumRowsOrColumns="10" Orientation="Horizontal" />
        </ItemsPanelTemplate>
    </GridView.ItemsPanel>
</GridView>

Answer 1

Bitmap from StorageItemThumbnail shows wrong dimensions in GridView

请参考GetThumbnailAsync document, The requested size, in pixels, of the longest edge of the thumbnail. Windows uses the requestedSize as a guide and tries to scale the thumbnail image without reducing the quality of the image. When you set ThumbnailMode as PicturesView并像下面这样调用GetThumbnailAsync方法

await destinationFile.GetThumbnailAsync(ThumbnailMode.PicturesView, 500, ThumbnailOptions.UseCurrentScale);

将图片裁剪为19 / 13，则宽度限制为500，高度限制为342。

针对您的场景，我们建议您使用 ThumbnailMode.SingleItem 替换上面并将图像拉伸属性设置为 Fill

StorageItemThumbnail thumbnail = await file.GetThumbnailAsync(ThumbnailMode.SingleItem, 500, ThumbnailOptions.ResizeThumbnail);

StorageItemThumbnail 中的位图在 GridView 中显示错误的尺寸

Bitmap from StorageItemThumbnail shows wrong dimensions in GridView

c#

gridview

image

uwp