Wpf Canvas Background image does not display selected image from local path
XAML Code
<Canvas x:Name="LayoutRoot" Margin="485,24,0,0" HorizontalAlignment="Left" Width="341" Height="506" VerticalAlignment="Top">
<Canvas.Background>
<ImageBrush ImageSource="{Binding BGImage}"/>
</Canvas.Background>
</Canvas>
MVVM code
private String _BGImage = #"C:/Users/sam/Desktop/photo-5.jpg";
public String BGImage
{
get
{
return this._BGImage;
}
set
{
this._BGImage = value;
NotifyPropertyChanged("BGImage");
}
}
Why this image not display on canvas background
or you can try using a converter
<UserControl.Resources>
<local:StringToImageConverter x:Key="StringToImageConverter" />
</UserControl.Resources>
...
<Canvas x:Name="LayoutRoot" Margin="485,24,0,0" HorizontalAlignment="Left" Width="341" Height="506" VerticalAlignment="Top">
<Canvas.Background>
<ImageBrush ImageSource="{Binding Path=BGImage, Converter={StaticResource StringToImageConverter}}"/>
</Canvas.Background>
</Canvas>
and this is the converter
public class StringToImageConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value.GetType() != typeof(string))
{
throw new InvalidOperationException("The value must be a string");
}
return new BitmapImage(new Uri((string)value));
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return null;
}
}
of course you would still need to check if the string is a valid URI
Your viewmodel code for BGImage should look something like this:
private ImageSource _BGImage = new BitmapImage(new Uri(#"C:\Users\sam\Desktop\photo-5.jpg", UriKind.Absolute))
public ImageSource BGImage
{
get { return _BGImage; }
set
{
_BGImage= value;
NotifyPropertyChanged("BGImage");
}
}
Well you need to have BGImage as BitmapImage rather than string
public BitmapImage BGImage
{
get
{
return new BitmapImage((new Uri(this._BGImage, UriKind.Absolute)));
}
}
If you are changing image dynamically then you have to raise property changed to notify UI
Related
I have multiple canvas images of different types (image source, geometry, path) and wish to only show 1 depending on a string binding.
whats the best way to do this?
i'd like it to be reusable so i can place this code inside a user control and then have many of these images around the app and i select which 1 is shown.
Like so:
<CanvasImage Image="Pie"/>
<CanvasImage Image="Dog"/>
Would it be too computationally expensive to have them all declared in the user control view and use visibility bindings
Pie canvas example:
<canvas>
<Data ="m24,98,07">
</canvas>
Dog canvas example:
<canvas>
<image source="">
<canvas>
This converter return an image source directly, depending on the value it receives.
namespace TestTreeView.Views
{
public class StringToImageConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string file = "";
string v = value as string;
switch (v)
{
case "Pie":
file = #".\path\to\your\pie.jpg";
break;
case "Dog":
file = #".\path\to\your\dog.jpg";
break;
default:
return null;
}
return new BitmapImage(new Uri(file, UriKind.RelativeOrAbsolute));
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
Usage in XAML:
<Window xmlns:local="clr-namespace:YourNamespace.Views" ...>
<Window.Resources>
<local:StringToImageConverter x:Key="stringToImageConverter"/>
</Window.Resources>
<Grid>
<Canvas>
<Image Source="{Binding YourString, Converter={StaticResource stringToImageConverter}}"/>
</Canvas>
</Grid>
</Window>
Original answer
I think you need to use a Converter.
It will take a ConverterParameter, a String, that will tell what the binded value is expected to be, and return a Visiblity to indicate if the canvas should be visible or not.
namespace YourNamespace.Views
{
public class StringToCanvasVisibilityConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
string v = value as string;
string p = parameter as string;
return (v != null && p != null && v == p) ? Visibility.Visible : Visibility.Collapsed;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
Usage in XAML:
<Window xmlns:local="clr-namespace:YourNamespace.Views" ...>
<Window.Resources>
<local:StringToVisibilityConverter x:Key="stringToVisibilityConverter"/>
</Window.Resources>
<Grid>
<Canvas Visibility="{Binding YourString, Converter={StaticResource stringToVisibilityConverter}, ConverterParameter=Pie}"/>
<Canvas Visibility="{Binding YourString, Converter={StaticResource stringToVisibilityConverter}, ConverterParameter=Dog}"/>
</Grid>
</Window>
I intend to create Usercontrol with boolean dependency property called IsPowerOn, When I change it True the PowerOn image load to Image.source and when I set IsPowerOn to Fals, the PowerOff image load to Image.source.
Here is my UserControl:
<UserControl x:Class="...UcPower"
...
<UserControl.Resources>
<local:PowerBoolean2Image x:Key="PowerBoolean2Image"/>
</UserControl.Resources>
<Grid>
<Image x:Name="imgPower" Source="{Binding Source, Converter={StaticResource PowerBoolean2Image}, Mode=OneWay, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:UcPower}}}" />
</Grid>
And Code behind:
public static readonly DependencyProperty IsPowerOnProperty = DependencyProperty.Register("IsPowerOn", typeof(bool), typeof(UcPower),
new FrameworkPropertyMetadata(false) { BindsTwoWayByDefault = true });
public bool IsPowerOn
{
get
{
return (bool)GetValue(IsPowerOnProperty);
}
set
{
SetValue(IsPowerOnProperty, value);
}
}
And IValueConverter:
public class PowerBoolean2Image : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (!(value is bool))
{
return null;
}
if (value.Equals(true))
{
// Power On
return new BitmapImage(new Uri("pack://application:,,,/Resources/Power-On.png"));
}
else
{
// Power Off
return new BitmapImage(new Uri("pack://application:,,,/Resources/Power-Off.png"));
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
But it doesn't work I expect, whats the wrong with me?
You should bind to the IsPowerOn property:
<Image Source="{Binding IsPowerOn, ...}" />
instead of
<Image Source="{Binding Source, ...}" />
Besides that, the expression if (value.Equals(true)) looks rather strange. You could replace that by
if ((bool)value)
{
return new BitmapImage(new Uri("pack://application:,,,/Resources/Power-On.png"));
}
return new BitmapImage(new Uri("pack://application:,,,/Resources/Power-Off.png"));
or shorter:
return (bool)value
? new BitmapImage(new Uri("pack://application:,,,/Resources/Power-On.png"))
: new BitmapImage(new Uri("pack://application:,,,/Resources/Power-Off.png"));
When I use this code in IValueConverter I get Error: IOException: Cannot locate resource 'resources/power-on.png'. and cant see my form in design mode:
Uri("pack://application:,,,/Resources/Power-On.png")
But I can use Assembly name to solve the problem like this code:
Uri("pack://application:,,,/ReferencedAssembly;component/Resources/Power-On.png")
I am displaying some image in my wpf app using following code:
<Image Source="{Binding Path=TemplateImagePath, Mode=TwoWay}" Grid.Row="3" Grid.Column="2" Width="400" Height="200"/>
and setting it's binding property inside code behind's constructor by navigating through some directory, below is the code:
DirectoryInfo Dir = new DirectoryInfo(#"D:/Template");
if (Dir.Exists)
{
if (Dir.GetFiles().Count() > 0)
{
foreach (FileInfo item in Dir.GetFiles())
{
TemplateImagePath = item.FullName;
}
}
}
but if user upload some other image then I need to delete this old image which is I am doing in the following way and setting image binding to null:
DirectoryInfo Dir = new DirectoryInfo(#"D:/Template");
if (Dir.Exists)
{
if (Dir.GetFiles().Count() > 0)
{
foreach (FileInfo item in Dir.GetFiles())
{
TemplateImagePath= null;
File.Delete(item.FullName);
}
}
}
But Iam getting exception that Cannot delete file used by some other process.
How can I delete it?
In order to be able to delete the image while it is displayed in an ImageControl, you have to create a new BitmapImage or BitmapFrame object that has BitmapCacheOption.OnLoad set. The bitmap will then be loaded from file immediately and the file is not locked afterwards.
Change your property from string TemplateImagePath to ImageSource TemplateImage and bind like this:
<Image Source="{Binding TemplateImage}"/>
The set the TemplateImage property like this:
BitmapImage image = new BitmapImage();
image.BeginInit();
image.CacheOption = BitmapCacheOption.OnLoad;
image.UriSource = new Uri(item.FullName);
image.EndInit();
TemplateImage = image;
or this:
TemplateImage = BitmapFrame.Create(
new Uri(item.FullName),
BitmapCreateOptions.None,
BitmapCacheOption.OnLoad);
If you want to keep binding to your TemplateImagePath property you may instead use a binding converter that converts the string to an ImageSource as shown above.
According to Clemens suggestion, here is the binding converter to have a good code-reuse:
namespace Controls
{
[ValueConversion(typeof(String), typeof(ImageSource))]
public class StringToImageSourceConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (!(value is string valueString))
{
return null;
}
try
{
ImageSource image = BitmapFrame.Create(new Uri(valueString), BitmapCreateOptions.IgnoreImageCache, BitmapCacheOption.OnLoad);
return image;
}
catch { return null; }
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
}
And there is a string for binding, for example
public string MyImageString { get; set; } = #"C:\test.jpg"
And in the UI the converter is used, in my case from the Library named "Controls"
<Window x:Class="MainFrame"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:controls="clr-namespace:Controls;assembly=Controls">
<Window.Resources>
<controls:StringToImageSourceConverter x:Key="StringToImageSourceConverter" />
</Window.Resources>
<Grid>
<Image Source="{Binding MyImageString, Converter={StaticResource StringToImageSourceConverter}}" />
</Grid>
</Window>
I have a combobox for selecting media types. I would like mediaelement's height to change when .vmw, .mpeg or .avi files are selected. How can I achieve this with MVVM approach?
Thanks in advance
You could bind the Width and Height of the MediaElement directly to its Source property with an appropriate converter, which selects the proper size depending on the media type:
<MediaElement
Width="{Binding Path=Source, RelativeSource={RelativeSource Self}, Converter={StaticResource MediaElementSizeConverter}, ConverterParameter=Width}"
Height="{Binding Path=Source, RelativeSource={RelativeSource Self}, Converter={StaticResource MediaElementSizeConverter}, ConverterParameter=Height}"/>
The converter:
public class MediaElementSizeConverter : IValueConverter
{
private const double defaultWidth = 320d;
private const double defaultHeight = 240d;
private const double wmvWidth = 640d;
private const double wmvHeight = 480d;
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
Uri source = value as Uri;
if (source != null)
{
if (source.AbsolutePath.EndsWith(".wmv"))
{
return (parameter as string) == "Width" ? wmvWidth : wmvHeight;
}
// more media types ...
}
return (parameter as string) == "Width" ? defaultWidth : defaultHeight;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
One solution would be to bind the ComboBox to a list of self created MediaTypeDefinition classes.
public class MediaTypeDefinition
{
public string Name { get; set; }
public int Height { get; set; }
}
You can then bind the SelectedItem to the height of the media element.
<ComboBox x:Name="mediaTypeList" ItemsSource="{Binding Definitions}" SelectedValuePath="Name" />
<MediaElement Height="{Binding SelectedItem.Height, Elementname=mediaTypeList}" />
I am looking for a way to be able to use the wpf Path element to draw a path that will represent a route on the map. I have the Route class that contains a collection of vertices and would like to use it for binding. I don't really know how to even start..
Any hints?
The main thing you'll need for the binding is a converter that turns your points into Geometry which the path will need as Data, here is what my one-way converter from a System.Windows.Point-array to Geometry looks like:
[ValueConversion(typeof(Point[]), typeof(Geometry))]
public class PointsToPathConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
Point[] points = (Point[])value;
if (points.Length > 0)
{
Point start = points[0];
List<LineSegment> segments = new List<LineSegment>();
for (int i = 1; i < points.Length; i++)
{
segments.Add(new LineSegment(points[i], true));
}
PathFigure figure = new PathFigure(start, segments, false); //true if closed
PathGeometry geometry = new PathGeometry();
geometry.Figures.Add(figure);
return geometry;
}
else
{
return null;
}
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotSupportedException();
}
#endregion
}
Now all that is really left is to create an instance of it and use it as the converter for the binding. What it might look like in XAML:
<Grid>
<Grid.Resources>
<local:PointsToPathConverter x:Key="PointsToPathConverter"/>
</Grid.Resources>
<Path Data="{Binding ElementName=Window, Path=Points, Converter={StaticResource ResourceKey=PointsToPathConverter}}"
Stroke="Black"/>
</Grid>
If you need the binding to update automatically you should work with dependency properties or interfaces like INotifyPropertyChanged/INotifyCollectionChanged
Hope that helps :D
Also you can try it this way:
public static class PathStrings
{
public const string Add = "F1 M 22,12L 26,12L 26,22L 36,22L 36,26L 26,26L 26,36L 22,36L 22,26L 12,26L 12,22L 22,22L 22,12 Z";
}
Then in the resource create a PathString
<Window.Resources>
<yourNamespace:PathStrings x:Key="pathStrings"/>
</Window.Resources>
then bind it this way:
<Path Stroke="Black" Fill="Black"
Data="{Binding Source={StaticResource pathStrings}, Path=Add}"></Path>