i just have to change my XAML definition:
<Canvas.Background>
<SolidColorBrush Color="White"/>
</Canvas.Background>
do not use Opacity="0" when you want to save your canvas into a jpeg - cause jpeg did not support opacity
Pregunta
I use a Windows.Control.Canvas in my application to get the signiture for the user. then i just want to save this signiture as jpeg picture.
however, when i save the picture the color seems to be inverted just for testing i also tried to save the picture as png - now the picture is as it should be!
I am using this code to save these pictures:
public static void SaveCanvasToJPEG(Canvas canvas)
{
Rect bounds = VisualTreeHelper.GetDescendantBounds(canvas);
RenderTargetBitmap rtb = new RenderTargetBitmap((int)(bounds.Width),
(int)(bounds.Height),
96d,
96d,
PixelFormats.Default);
DrawingVisual dv = new DrawingVisual();
using (DrawingContext ctx = dv.RenderOpen())
{
VisualBrush vb = new VisualBrush(canvas);
ctx.DrawRectangle(vb, null, new Rect(new Point(), bounds.Size));
}
rtb.Render(dv);
//endcode as PNG
JpegBitmapEncoder jpegEncoder = new JpegBitmapEncoder();
FormatConvertedBitmap convertImg2GrayScale = new FormatConvertedBitmap(rtb, PixelFormats.Gray16, null, 0);
jpegEncoder.Frames.Add(BitmapFrame.Create(convertImg2GrayScale));
// *********** TESTING (begin) ************
System.IO.MemoryStream ms2 = new System.IO.MemoryStream();
PngBitmapEncoder pngEncoder = new PngBitmapEncoder();
pngEncoder.Frames.Add(BitmapFrame.Create(rtb));
pngEncoder.Save(ms2);
ms2.Close();
System.IO.File.WriteAllBytes("logo.png", ms2.ToArray());
// *********** TESTING (end) ************
//save to memory stream
System.IO.MemoryStream ms = new System.IO.MemoryStream();
jpegEncoder.Save(ms);
ms.Close();
System.IO.File.WriteAllBytes("logo.jpg", ms.ToArray());
}
an here is the XML:
<UserControl x:Class="WPF_App.SignControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="600" d:DesignWidth="1252" Loaded="_eventUserControlLoaded">
<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition Height="0*"/>
</Grid.RowDefinitions>
<Border BorderBrush="Black" BorderThickness="1" HorizontalAlignment="Left" Height="330" Margin="159,149,0,0" VerticalAlignment="Top" Width="935"/>
<Canvas x:Name="canSignPad" Focusable="True" HorizontalAlignment="Left" Height="328" Margin="160,150,0,0"
ScrollViewer.VerticalScrollBarVisibility="Disabled" VerticalAlignment="Top" Width="933"
MouseDown="_canvasMouseDown" MouseMove="_canvasMouseMove">
<Canvas.Background>
<SolidColorBrush Color="White" Opacity="0"/>
</Canvas.Background>
</Canvas>
</Grid>
</UserControl>
i found a lot of posts talking about jpeg pictures come out blue, but i did not find a solution for my problem.
Solución
i just have to change my XAML definition:
<Canvas.Background>
<SolidColorBrush Color="White"/>
</Canvas.Background>
do not use Opacity="0" when you want to save your canvas into a jpeg - cause jpeg did not support opacity