本帖最后由 crycry12345 于 2017-1-29 23:19 编辑

我知道問題出在哪了，canvas要給他明確的width和height值，然後後台再根據需要修改值，感謝大家!

2017/1/29
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最近在研究微軟人臉識別，用了一個Viewbox來等比例縮放，結果顯示不出東西，測試了一下發現Canvas放在Viewbox裡rectangle就無法顯示，
但是我需要把canvas放進viewbox，這樣才可以對rectangle進行縮放。請問是哪出問題了?我用的是VS2017RC

<Page
x:Class="ComputerVision.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:ComputerVision"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">

<Grid x:Name="root" Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="2*"/>
<ColumnDefinition Width="1*"/>
</Grid.ColumnDefinitions>

<Grid x:Name="pictureDisplay" Background="Black" Grid.Column="0">
<Viewbox Stretch="Uniform" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<Canvas x:Name="canvas" Width="{x:Bind selectedImage.Width,Mode=OneWay}" Height="{x:Bind selectedImage.Height,Mode=OneWay}">
<Image x:Name="selectedImage" Source="/Assets/Square150x150Logo.scale-200.png" Stretch="Uniform"/>
</Canvas>
</Viewbox>
</Grid>

<Grid x:Name="textAndButton" Background="AliceBlue" Grid.Column="1">
<Grid.RowDefinitions>
<RowDefinition Height="9*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<TextBlock x:Name="resultText" Text="" TextWrapping="Wrap" FontSize="30" VerticalAlignment="Top" HorizontalAlignment="Left" Grid.Row="0"/>
<Button x:Name="pickButton" Content="Pick Picture" VerticalAlignment="Center" HorizontalContentAlignment="Center" Grid.Row="1" Click="pickButton_Click"/>
</Grid>
</Grid>
</Page>