I have a function receiving a Drawing that I need to partially expose as a DrawingImage (i.e.: its position and size will be reduced/changed to fit in a target area).
How can I crop/clip a region of the original Drawing?
Or maybe it is easier to do that after the transformation to DrawingImage (how clip that DrawingImage)?
The solution was to encapsulate the original Drawing in a DrawingGroup and then apply a clipping geometry...
public DrawingGroup MyClippingFunc(Drawing OriginalDrawing, Rect ClippingArea)
{
var Group = new DrawingGroup();
Group.Children.Add(OriginalDrawing);
Group.ClipGeometry = new RectangleGeometry(ClippingArea);
return Group;
}
This is another way to do it, using the InkCanvas StrokeCollection class as an example.
using (DrawingContext drawingContext = drawingGroup.Open())
{
drawingContext.PushClip(new RectangleGeometry(yourRectangleObject));
Strokes.Draw(drawingContext);
drawingContext.Pop();
}
I am a little confused on what you are asking but maybe my answer to this similar question will help?
How can I use a PathGeometry as a mask for a BitmapSource (or any image data)?
Related
So I have an InkCanvas to which I have added "custom strokes".
I am at a complete loss as to how to erase custom strokes added to the InkCanvas through its DrawingContext. (Google has been of no help:( ) Making the assumption that I have a bounding rectangle for the area on the InkCanvas I want to erase, how can this be done?
(I am quickly coming to the conclusion that once something is drawn on the DrawingContext it can not be removed -- only convered :( ).
The Custom Strokes are created in the standard way by overriding the DrawCore method of the Stroke, e.g.,
// Draw Rectangle
public class RectangleStroke : Stroke
{
// Constructor
public RectangleStroke(StylusPointCollection pts)
: base(pts)
{
StylusPoints = pts;
}
protected override void DrawCore(DrawingContext drawingContext, DrawingAttributes drawingAttributes)
{
if (drawingContext == null)
{
throw new ArgumentNullException("drawingContext");
}
if (null == drawingAttributes)
{
throw new ArgumentNullException("drawingAttributes");
}
DrawingAttributes originalDa = drawingAttributes.Clone();
SolidColorBrush brush = new SolidColorBrush(drawingAttributes.Color);
brush.Freeze();
Pen pen = new Pen(brush, 1);
StylusPoint stp = StylusPoints[0];
StylusPoint sp = StylusPoints[1];
drawingContext.DrawRectangle(brush, pen, new Rect(new Point(sp.X, sp.Y), new Point(stp.X, stp.Y)));
}
}
Similar methods results in a picture like:
How are custom strokes erased knowing only the bounding rectangle?
Thanks for any help or suggestions.
Ugh...What should have been obvious is that the custom strokes inherit from Stroke and even though a datacontext once written can not be unwritten, the InkCanvas can erase its strokes--including custom strokes--by changing the InkCanvasEditingMode to EraseByStroke. Hope this helps somebody.
I am using C#, Silverlight, Visual Studio for Windows Phone 7.
I would like to get the Clip of a UIElement that includes any transform that has been done on the UIElement.
This example gives me the Clip but does not include any transform from the UIElement:
// uie is a UIElement taken from a PhoneApplicationPage
Geometry myClip = uie.Clip;
I tried the following, but it ended up moving the UIElement:
var frame = Application.Current.RootVisual as PhoneApplicationFrame;
var page = frame.Content as PhoneApplicationPage;
GeneralTransform gt = uie.TransformToVisual(page);
uie.RenderTransform = gt as Transform;
Geometry myClip = uie.Clip;
I also tried to add an inverse transform at the end to undo any movement, but that seemed to make it worse:
uie.RenderTransform = gt.Inverse as Transform;
Please help me get the Clip with the original transform of the UIElement without messing with the UIElement itself.
Thanks in advance.
I figured out how to solve this without messing with the original UIElement. I needed to create a new Geometry object with the same data rather than using the original Geometry. Not only does this separate the new data from the old data, it also prevents an object from possibly getting assigned as a child to multiple objects.
Here is the resulting code I used:
var frame = Application.Current.RootVisual as PhoneApplicationFrame;
var page = frame.Content as PhoneApplicationPage;
GeneralTransform gt = uie.TransformToVisual(page);
var place = gt.Transform(new Point());
// declaring new variables to hold these values
Geometry geom;
Path path = new Path();
// here I checked for other restrictions on my UIElements before assigning the variables
geom = new RectangleGeometry();
(geom as RectangleGeometry).Rect = new Rect(place.X, place.Y, uie.RenderSize.Width, uie.RenderSize.Height);
path.Data = geom;
I mentioned that I check for some restrictions on my UIElements before assigning the variables. This is related to another question I posted about clips (here).
I am working with DrawingVisual in WPF and want to make some Effect.
Is it possible to brush a DrawingVisual with any brushes? That means:
Suppose I have a DrawingVisual:
DrawingVisual myVisual = new DrawingVisual();
myVisual.RenderOpen().....
.....
....
....
No matter how I draw, I want to make the whole visual to be in a color brush at the end.
something like: drawingcontext.drawvisual(myVisual, Brushes.Red) ??
Thank you.
A DrawingVisual is not itself a drawing object that can be filled with a Brush or outlined with a Pen. Instead it is a container for Drawing objects (and for other visuals, since it is also a ContainerVisual).
If you want to "fill" a DrawingVisual with a "background" brush, you would have to draw an appropriate Drawing, e.g. a large enough filled rectangle.
I'm using a Silverlight Bing Maps Control, and have defined a number of MapPolygon areas as children to the map control.
What I want ideally, is the ability to add a TextBlock label to the center of the interior of the MapPolygon.
How should I go about doing this?
If you only need an approximate center of the polygon, you can find the center of its bounding box and programatically add a TextBlock over the polygon.
So something like this might work:
(XAML)
<MapControl:Map x:Name="MyMap">
<MapControl:Map.Children>
<MapControl:MapPolygon Fill="Red" Stroke="Yellow" StrokeThickness="5" Opacity="0.7">
<MapControl:MapPolygon.Locations>
<m:LocationCollection>
<m:Location>20, -20</m:Location>
<m:Location>20, 20</m:Location>
<m:Location>-20, 20</m:Location>
<m:Location>-20, -20</m:Location>
</m:LocationCollection>
</MapControl:MapPolygon.Locations>
</MapControl:MapPolygon>
</MapControl:Map.Children>
</MapControl:Map>
(Codebehind)
public partial class MainPage : UserControl
{
private MapLayer tbLayer;
public MainPage()
{
InitializeComponent();
tbLayer = new MapLayer();
List<TextBlock> newTbs = new List<TextBlock>();
// loop through the maps children and find the polygons
foreach (var child in MyMap.Children)
{
if (child is MapPolygon)
{
var poly = child as MapPolygon;
// get the average lat and long to calculate the "center"-ish of the polygon
var avgLat = poly.Locations.Select(l => l.Latitude).Average();
var avgLon = poly.Locations.Select(l => l.Longitude).Average();
TextBlock tb = new TextBlock
{
Text = "Hey there. I'm a polygon."
};
// set the position of the textblock and add it to a new map layer
MapLayer.SetPositionOrigin(tb, PositionOrigin.Center);
MapLayer.SetPosition(tb, new Location(avgLat, avgLon));
tbLayer.Children.Add(tb);
}
}
// add the new maplayer to the parent map
MyMap.Children.Add(tbLayer);
}
}
If your polygons are oddly shaped and not nice little squares like my generic example, then you might need to get a little dirtier. In which case, you may need a web service (WCF) that can calculate your centroid of the polygon. I don't think theres a simple way in Silverlight to do this.
It would be a process similar to the following:
Send the points to a WCF service method.
Load up a SqlGeometry object with your points, probably by forming WKT with those points and using SqlGeometry.Parse
Call STCentroid on your SqlGeometry object.
return SqlGeometry.STAsText to return the WKT of the point you just got by calling STCentroid.
It's a bit of a mess, but doing spatial stuff in Silverlight is always messy in my experience.
Hope that helps and wasn't too long winded :)
in my custom control i have a ContainerVisual object and a DrawingVisual under it.
I override ArrangeOverride and calculate the rectangle that i want to draw in based on the given size and the control's padding.
after that i set my ContainerVisual object's transform to the upper left corner of the rectangle so that the methods that render the drawing would not have to take account of the rectangle and assume that the drawing origin is at point 0,0.
this does not work, and the drawing is displaced. if instead i set transform of the DrawingVisual object it works and the rectangle is displayed the way it is supposed to be.
i thought that if i set transform on the container, it will automatically be applied to the visuals under it. is that so?
thanks for any help
EDIT: Updated the source code to show complete code.
class MyControl : Control
{
private readonly ContainerVisual container = new ContainerVisual();
private readonly DrawingVisual drawing = new DrawingVisual();
private Rect rect;
private void RenderDrawing()
{
using (var c = drawing.RenderOpen())
{
var p = new Pen(new SolidColorBrush(Colors.Black), 1);
c.DrawRectangle(null, p, new Rect(0, 0, rect.Width, rect.Height));
}
}
protected override Size ArrangeOverride(Size s)
{
var h = Math.Max(0, s.Height - Padding.Top - Padding.Bottom);
var w = Math.Max(0, s.Width - Padding.Left - Padding.Right);
var r = new Rect(Padding.Left, Padding.Top, w, h);
if (rect != r)
{
rect = r;
container.Clip = new RectangleGeometry(rect);
container.Transform = new TranslateTransform(rect.Left, rect.Top);
// replace the line above with the following line to make it work
// drawing.Transform = new TranslateTransform(rect.Left, rect.Top);
RenderDrawing();
}
return s;
}
protected override Visual GetVisualChild(int index)
{
return container;
}
protected override Size MeasureOverride(Size s)
{
return new Size();
}
protected override int VisualChildrenCount
{
get { return 1; }
}
public MyControl()
{
container.Children.Add(drawing);
AddVisualChild(container);
}
}
<Window x:Class="MyApp.MyWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:c="clr-namespace:MyApp"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Grid>
<c:MyControl Padding="20" />
</Grid>
</Window>
Explanation of strange clipping behavior
Now that you have posted your full source code I was finally able to see what you were seeing. Your problem isn't in the transform at all: It is in the clip!
If you comment out the container.Clip assignment statement, you get identical results no matter whether you put the transform on container or drawing
If you uncommented container.Clip assignment statement, the clipping region is perfectly centered on when the drawing is transformed, but when the container is transformed the clipping area is offset, so that only the lower and right lines of the rectangle were visible (and not all of those)
The reason this occurs is that the geometry specified for container.Clip is part of the container, so it is affected by container.Transform but not drawing.Transform:
This can be better understood by looking at the upper-left corners of the container, drawing, rectangle, and clip area relative to the upper-left corner of the window:
When you set the transform on the drawing:
Container is at (0,0) relative to window (null transform)
Clip area is at (20,20) relative to window (null transform + RectangleGeometry)
Drawing is at (20,20) relative to window (null transform + TranslateTransform)
Rectangle is at (20,20) relative to window (null transform + TranslateTransform + 0,0)
When you set the transform on the container:
Container is at (20,20) relative to window (TranslateTransform)
Clip area is at (40,40) relative to window (TranslateTransform + RectangleGeometry)
Drawing is at (20,20) relative to window (TranslateTransform + null transform)
Rectangle is at (20,20) relative to window (TranslateTransform + null transform + 0,0)
So your problem isn't that the transform isn't happening: It is that the transform is moving the clip area too, so the clip area no longer coincides with the rectangle and you can only see two sides of the rectangle.
Answer given for original code (retained because it has some useful explanation)
In fact, the code you posted never uses "container" so all you will see is a blank screen.
In your actual code you are using "container" incorrectly, preventing the events from occurring in the correct sequence to cause its Transform to be picked up and passed to the MIL layer.
Remember that when a Visual has a Transform set, it is not the visual itself but that Visual's visual parent that actually handles that transform. For example, if you render a page to XPS using ReachFramework or do hit testing, the Transform on the outermost Visual is ignored.
Your understanding is correct: If your visual tree is built following all the rules, it doesn't matter whether your transform is on your "container" or your "drawing".
Since you are using Control anyway, I'm curious why you don't just let the normal UIElement-based layout system handle your layout needs.
First update (retained for the same reason)
Thanks for the code correction. It is as I suspected: You are building your visual tree incorrectly. If you are using AddVisualChild you also must also override GetVisualChild and VisuaChildrenCount. This is because Visual does not store a list of children: It is up to the subclass (your class) to do this. What is happening is:
When you call AddVisualChild the container's transform is null so that is what is passed down to MILCore.
Later when you change the container's transform, it uses its parent pointer (that was set in AddVisualChild) to signal that its transform data must be refreshed. This update requires part of the visual tree to be scanned using GetVisualChild and VisualChildrenCount.
Since you didn't implement these methods this part of the update fails.
You say you are "new to WPF." Are you aware that you are playing with some of WPF's most low-level and esoteric features, ones that would never be used in a most ordinary WPF applications? It is equivalent to starting to learn programming using machine language. Normally you would use templates with Path, Rectangle, etc for this purpose. Sometimes you might go lower level and use a DrawingBrush with a DrawingGroup containing GeometryDrawings, etc. But you would almost never go all the way down to DrawingVisual and RenderOpen! The only time you would do that is when you have huge drawings consisting of millions of individual items and so you want to bypass all the layout and structure overhead of the higher layers for absolute maximum performance.
Manipulating the visual tree yourself (AddVisualChild, etc) is also an advanced feature. I always recommend people new to WPF stick with UIElement and above for the first few months, using Control with templates. I recommend they use Path and other shape subclasses for their drawings, and use VisualBrushes when advanced drawing effects are needed.
Hope this helps.
the problem is with the container.Clip. it should be
container.Clip = new RectangleGeometry(new Rect(0, 0, w, h));