Scaling an Image

Scaling helps in resizing (reducing and enlarging the size) of an image by changing the number of pixels in the image. Bitmap provides Scaler class for scaling an image. The Scaler class requires three properties to scale an image, which are as follows:

DestinationWidth: The destination width.
DestinationHeight: The destination height.
InterpolationMode: The interpolation mode to use when scaling.

The GIF given below shows scaling in and out of an image.

The following code implements scaling in on a button click event and scaling out on another button's click event. The example uses the sample created in Quick Start.

Visual Basic
C#

Visual Basic

Private Async Function UpdateImageSource() As Task
    Dim sb As SoftwareBitmap = btmp.ToSoftwareBitmap()
    sbs = New SoftwareBitmapSource()
    Await sbs.SetBitmapAsync(sb)
    img.Source = sbs

    img.Width = btmp.PixelWidth
    img.Height = btmp.PixelHeight
End Function

Private Async Function ApplyTransform(t As BaseTransform) As Task
    Dim bm = btmp.Transform(t)
    btmp.Dispose()
    btmp = bm
    Await UpdateImageSource()
End Function

Private Async Sub btnScale_Click(sender As Object, e As RoutedEventArgs)
    Dim px As Integer = btmp.PixelWidth * 1.6F + 0.5F
    Dim py As Integer = btmp.PixelHeight * 1.6F + 0.5F
    Await ApplyTransform(New Scaler(px, py, InterpolationMode.HighQualityCubic))
End Sub


Private Async Sub btnScaleOut_Click(sender As Object, e As RoutedEventArgs)
    Dim px As Integer = btmp.PixelWidth * 0.625F + 0.5F
    Dim py As Integer = btmp.PixelHeight * 0.625F + 0.5F
    If px > 0 AndAlso py > 0 Then
        Await ApplyTransform(New Scaler(px, py, InterpolationMode.HighQualityCubic))
    End If
End Sub

private async Task UpdateImageSource()
{
    SoftwareBitmap sb = btmp.ToSoftwareBitmap();
    sbs = new SoftwareBitmapSource();
    await sbs.SetBitmapAsync(sb);
    img.Source = sbs;
    
    img.Width = btmp.PixelWidth;
    img.Height = btmp.PixelHeight;
}
        
private async Task ApplyTransform(BaseTransform t)
{
    var bm = btmp.Transform(t);
    btmp.Dispose();
    btmp = bm;
    await UpdateImageSource();
}
        
private async void btnScale_Click(object sender, RoutedEventArgs e)
{
    int px = (int)(btmp.PixelWidth * 1.6f + 0.5f);
    int py = (int)(btmp.PixelHeight * 1.6f + 0.5f);
    await ApplyTransform(new Scaler(px, py, InterpolationMode.HighQualityCubic));
}

private async void btnScaleOut_Click(object sender, RoutedEventArgs e)
{
    int px = (int)(btmp.PixelWidth * 0.625f + 0.5f);
    int py = (int)(btmp.PixelHeight * 0.625f + 0.5f);
    if (px > 0 && py > 0)
    {
        await ApplyTransform(new Scaler(px, py, InterpolationMode.HighQualityCubic));
    }
}