Develop Reference

Cover an image with black and reveal parts of the image using mouse

So I am creating a "Map Viewer" for a program I am working on. Basically I want to display a map and have it resize the image to fit in the grid. For this I am using Viewbox to hold the image and resize it. I was attempting to use this code to reveal the map but it does not center the circle on the mouse and it does not retain the revealed portions of the map (it ONLY reveals where the mouse is and not where it has been).
Here is the XAML:
<Viewbox x:Name="MapHolder" Grid.Column="0" Grid.Row="0" Grid.ColumnSpan="1" Grid.RowSpan="7" Margin="25,5,25,15">
<Image x:Name="SelectedMap" Source="/wizard_dungeon.jpg" Stretch="Uniform" MouseMove="SelectedMap_MouseMove" >
<Image.OpacityMask>
<VisualBrush Stretch="None" >
<VisualBrush.Visual>
<Ellipse Width="400" Height="400" StrokeThickness="1" Fill="Black"/>
</VisualBrush.Visual>
<VisualBrush.RelativeTransform>
<TransformGroup>
<TranslateTransform x:Name="OpacityFilterTransform" X="1" Y="1"/>
</TransformGroup>
</VisualBrush.RelativeTransform>
</VisualBrush>
</Image.OpacityMask>
</Image>
</Viewbox>
And the code-behind:
private void SelectedMap_MouseMove(object sender, MouseEventArgs e)
{
var position = e.GetPosition(this);
var height = MapHolder.ActualHeight;
var width = MapHolder.ActualWidth;
// with the position values, interpolate a TranslateTransform for the opacity mask
var transX = position.X / width;
var transY = position.Y / height;
OpacityFilterTransform.X = transX - 0.5;
OpacityFilterTransform.Y = transY - 0.5;
}
I want there to basically be a Image under a Black screen and I can erase the black screen to reveal the image in the areas I have erased.

WPF Canvas Fill

I currently have a WPF windows with a Canvas is 600 x 400. Is it possible to scale or automatically zoom in so that the lines take up as much as the 600x600 as possible?
<Border>
<Canvas x:Name="cMap" Width="600" Height="400">
<Line X1="5" Y1="5" X2 ="10" Y2="10" StrokeThickness="2" Stroke="Black"/>
<Line X1="10" Y1="10" X2 ="15" Y2="25" StrokeThickness="2" Stroke="Black"/>
</Canvas>
</Border>
My intention will be to add lines programmatically via code instead of XAML.
Thanks.

Not sure what is your exact usecase, but you could probably benefit by using ViewBox:
<Border>
<Viewbox Stretch="Uniform">
<Canvas x:Name="cMap" Width="15" Height="25">
<Canvas.LayoutTransform>
<ScaleTransform />
</Canvas.LayoutTransform>
<Line X1="5" Y1="5" X2 ="10" Y2="10" StrokeThickness="2" Stroke="Black"/>
<Line X1="10" Y1="10" X2 ="15" Y2="25" StrokeThickness="2" Stroke="Black"/>
</Canvas>
</Viewbox>
</Border>

Hope this helps you!
To draw lines in code you shoud do something like this:
Line line = new Line();
Thickness thickness = new Thickness(101,-11,362,250);
line.Margin = thickness;
line.Visibility = System.Windows.Visibility.Visible;
line.StrokeThickness = 4;
line.Stroke = System.Windows.Media.Brushes.Black;
line.X1 = 10;
line.X2 = 40;
line.Y1 = 70;
line.Y2 = 70;
and don't forget to add:
myCanvas.Children.Add(line);
to put those line in some place
from: Drawing lines in code using C# and WPF
To resize your canvas please read this:
Canvas is the only panel element that has no inherent layout
characteristics. A Canvas has default Height and Width properties of
zero, unless it is the child of an element that automatically sizes
its child elements. Child elements of a Canvas are never resized, they
are just positioned at their designated coordinates. This provides
flexibility for situations in which inherent sizing constraints or
alignment are not needed or wanted. For cases in which you want child
content to be automatically resized and aligned, it is usually best to
use a Grid element.
So as a solution you would make it inside a GRID or using the following code:
public class CanvasAutoSize : Canvas
{
protected override System.Windows.Size MeasureOverride(System.Windows.Size constraint)
{
base.MeasureOverride(constraint);
double width = base
.InternalChildren
.OfType<UIElement>()
.Max(i => i.DesiredSize.Width + (double)i.GetValue(Canvas.LeftProperty));
double height = base
.InternalChildren
.OfType<UIElement>()
.Max(i => i.DesiredSize.Height + (double)i.GetValue(Canvas.TopProperty));
return new Size(width, height);
}
}
at your XAML:
<local:CanvasAutoSize VerticalAlignment="Top" HorizontalAlignment="Left"></local:CanvasAutoSize>
from: WPF: How to make canvas auto-resize?

Zoom In on Canvas - C#

I currently have a canvas that I load an image on in my program, and I would like to be able to right-click on a certain point on that image and click zoom in to zoom in on that point.
One solution I found was:
<Canvas>
<Canvas.RenderTransform>
<ScaleTransform ScaleX="2" ScaleY="2">
</Canvas.RenderTransform>
</Canvas>
This works however it doesn't zoom in to the specific coordinates but rather just zooms in to the top-left of the image. How would I implement coordinate zooming? zooming in on specific coordinates?

Using three separate transforms. One to move the canvas so that the click point is the origin. The second transform to scale and the third to put the click point back at the center again
<Canvas.RenderTransform>
<TransformGroup>
<TranslateTransform X="0" Y="0" />
<ScaleTransform ScaleX="1" ScaleY="1" />
<TranslateTransform X="0" Y="0" />
</TransformGroup>
</Canvas.RenderTransform>
private void Image_MouseDown(object sender, MouseButtonEventArgs e)
{
Point p = e.GetPosition(this);
var transformGroup = ImageCanvas.RenderTransform as TransformGroup;
var moveToOriginTransform = transformGroup.Children[0] as TranslateTransform;
var scaleTransform = transformGroup.Children[1] as ScaleTransform;
var moveBackTransform = transformGroup.Children[2] as TranslateTransform;
moveToOriginTransform.X = -p.X;
moveToOriginTransform.Y = -p.Y;
scaleTransform.ScaleX += 1;
scaleTransform.ScaleY += 1;
moveBackTransform.X = p.X;
moveBackTransform.Y = p.Y;
}

How to rotate an image within a StackPanel or Grid in Silverlight

I have an image control sits inside a Grid control. I already have a button to enable zoom-in to this image. After zoom-in, the Horizontal/vertical scroll bars are displayed. And then I rotate the image contained grid, the image and the grid scroll bar are messed up. How should I incorporate both zoom-in and rotate for the image control? The following are the code that I am using in my project.
The image control zoom-in code I used (x is the image control):
if ((x as Image) != null) { x.Height = x.Height * 1.3; x.Width = x.Width * 1.3; }
The rotation code I used (x is the image control):
if ((x as Image) != null)
{
RotateTransform rotate = new RotateTransform(); rotate.Angle = rotateAngle;
rotate.CenterX = x.Width / 2;
rotate.CenterY = x.Height / 2;
x.RenderTransform = rotate;
};
The XAML is:
<ScrollViewer x:Name="scrollViewer" Height="480" Width="615"
VerticalScrollBarVisibility="Auto"
HorizontalScrollBarVisibility="Auto">
<ScrollViewer.Content>
<Grid x:Name="ImageGrid">
<StackPanel x:Name="ImageStackPanel">
<Image Source="..." VerticalAlignment="Center" Width="220" Height="170" ></Image>
</StackPanel>
</Grid>
</ScrollViewer.Content>
</ScrollViewer>
Does anybody have any existing code snippet that I can borrow to resolve this trick?

I think you need to use TransformGroup to use more than one transform at the time:
ScaleTransform myScaleTransform = new ScaleTransform();
myScaleTransform.ScaleY = 3;
RotateTransform myRotateTransform = new RotateTransform();
myRotateTransform.Angle = 45;
// Create a TransformGroup to contain the transforms
// and add the transforms to it.
TransformGroup myTransformGroup = new TransformGroup();
myTransformGroup.Children.Add(myScaleTransform);
myTransformGroup.Children.Add(myRotateTransform);
// Associate the transforms to the image.
x.RenderTransform = myTransformGroup;

This may work for your needs:
<Image x:Name="image" Source="myImageSource" Stretch="Uniform"
HorizontalAlignment="Center" VerticalAlignment="Center"
RenderTransformOrigin="0.5, 0.5">
<Image.RenderTransform>
<TransformGroup>
<RotateTransform x:Name="Rotate"/>
<ScaleTransform x:Name="Scale" />
</TransformGroup>
</Image.RenderTransform>
</Image>
code behind:
Rotate.Angle = 45;
Scale = 0.25;

You may be missing the LayoutTransformer from the Silverlight Toolkit, and the AnimationMediator from one of the Toolkit developers.
With the LayoutTransformer you can set its content to anything, not just images, and apply any transformation with it, and as opposed to the usual RenderTransform, it will affect layout and actual sizes.
I have a similar scenario and I use it like this:
<Grid>
<fs:AnimationMediator x:Name="RotateMediator" LayoutTransformer="{Binding ElementName=LayoutTransformer}" AnimationValue="{Binding Angle, ElementName=RotateTransform, Mode=TwoWay}" />
<fs:AnimationMediator x:Name="ScaleXMediator" LayoutTransformer="{Binding ElementName=LayoutTransformer}" AnimationValue="{Binding ScaleX, ElementName=ScaleTransform, Mode=TwoWay}" />
<fs:AnimationMediator x:Name="ScaleYMediator" LayoutTransformer="{Binding ElementName=LayoutTransformer}" AnimationValue="{Binding ScaleY, ElementName=ScaleTransform, Mode=TwoWay}" />
<tkt:LayoutTransformer x:Name="LayoutTransformer" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<tkt:LayoutTransformer.LayoutTransform>
<TransformGroup>
<RotateTransform x:Name="RotateTransform" />
<ScaleTransform x:Name="ScaleTransform" />
</TransformGroup>
</tkt:LayoutTransformer.LayoutTransform>
<Image x:Name="MyImage" Source="mysource.png" Width="600" Height="800" />
</tkt:LayoutTransformer>
</Grid>
Because of the lack of MultiBinding you'd probably additionally have to manually handle the input value (from Slider controls etc) changed events and then set the AnimationValues of RotateMediator etc accordingly.

Rotate image (control) in Silverlight with Transform

I'm trying to rotate an image in Silverlight and can't seem to get it right. I've tried a few different ways so far and can't find the answer.
<Image Opacity=".5" x:Name="compassImg" Source="compass.png">
<Image.RenderTransform>
<RotateTransform x:Name="compassRotator"></RotateTransform>
</Image.RenderTransform>
</Image>
+
void compass_CurrentValueChanged(object sender, SensorReadingEventArgs<CompassReading> e)
{
Dispatcher.BeginInvoke(() =>
{
compassRotator.Angle = e.SensorReading.TrueHeading;
});
}
and
<Image Opacity=".5" x:Name="compassImg" Source="compass.png"></Image>
+
void compass_CurrentValueChanged(object sender, SensorReadingEventArgs<CompassReading> e)
{
Dispatcher.BeginInvoke(() =>
{
compassImg.RenderTransform = new CompositeTransform()
{
CenterX = 0.5,
CenterY = 0.5,
Rotation = e.SensorReading.TrueHeading
};
//OR (variations with 0.5 and width / 2 for both composite and rotate
compassImg.RenderTransform = new RotateTransform()
{
CenterX = compassImg.Width / 2,
CenterY = compassImg.Height / 2,
Angle = e.SensorReading.TrueHeading
};
});
}
It rotates, but it always rotates around 0/0. What am I doing wrong?

I looked up MSDN, and the second form is correct. http://msdn.microsoft.com/en-us/library/system.windows.media.rotatetransform.centerx.aspx (It is the coordinates, not fraction).
However, if you put a breakpoint where you apply the transform, you may find that Width is NaN. This is because width wasn't set. What you want is the ActualWidth.
One good way for exploration of transforms is to paste the following snippet into your XAML and experiment away.
<StackPanel HorizontalAlignment="Left">
<TextBlock>Center X</TextBlock>
<Slider
Name="RTX" Minimum="0.0" Maximum="116" />
<TextBlock>Center Y</TextBlock>
<Slider
Name="RTY" Minimum="0.0" Maximum="800"/>
<TextBlock>Angle</TextBlock>
<Slider
Name="Angle" Minimum="0.0" Maximum="360" />
</StackPanel>
<Image Source="{Binding ImagePath}" Name="image1">
<Image.RenderTransform>
<RotateTransform Angle="{Binding ElementName=Angle,Path=Value}"
CenterX="{Binding ElementName=RTX, Path=Value}"
CenterY="{Binding ElementName=RTY, Path=Value}"/>
</Image.RenderTransform>
</Image>

You need to set the RenderTransformOrigin Property to "0.5, 0.5", this will rotate the element around its centre.