如何在WPF中组合画笔？

Question

I have two brushes. I don't know wath type of brushes they are. They can be ImageBrushes, SolidBrushes or VisualBrushes. I have each in a variable of the "Brush" type.

I need to combine two brushes. How do I do it?

I tried this. But It didn't work. Here are Back and Front the brushes that need to me combined.

Border Bd = new Border();
Border Bdr = new Border();

Bd.Width = 1.0;
Bd.Height = 1.0;

Bd.Background = Back;
Bdr.Background = Front;

Bd.Child = Bdr;

Brush VB = new VisualBrush(Bd);

I need this because I am making a custom animation class to animate brushes. After making some test's I concluded that the error is in the combining of the brushes and not elsewhere in the class.

The resulting brush is completely transparent.

---

[EDIT]

Here is the complete BrushAnimation Class.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Media.Animation;
using System.Windows;
using System.Windows.Media;
using System.Windows.Controls;

namespace WPFSoPaTest
{
    class BrushAnimation : AnimationTimeline
    {
                protected override Freezable CreateInstanceCore()
        {
            return new BrushAnimation();
        }
        public override Type TargetPropertyType
        {
            get { return typeof(Brush); }
        }
        static BrushAnimation()
        {
            FromProperty = DependencyProperty.Register("From", typeof(Brush),
                typeof(BrushAnimation));

            ToProperty = DependencyProperty.Register("To", typeof(Brush),
                typeof(BrushAnimation));
        }
        public static readonly DependencyProperty FromProperty;
        public Brush From
        {
            get
            {
                return (Brush)GetValue(BrushAnimation.FromProperty);
            }
            set
            {
                SetValue(BrushAnimation.FromProperty, value);
            }
        }
        public static readonly DependencyProperty ToProperty;
        public Brush To
        {
            get
            {
                return (Brush)GetValue(BrushAnimation.ToProperty);
            }
            set
            {
                SetValue(BrushAnimation.ToProperty, value);
            }
        }
        public override object GetCurrentValue(object defaultOriginValue,
        object defaultDestinationValue, AnimationClock animationClock)
        {
            Brush fromVal = ((Brush)GetValue(BrushAnimation.FromProperty)).CloneCurrentValue();
            Brush toVal = ((Brush)GetValue(BrushAnimation.ToProperty)).CloneCurrentValue();

            if ((double)animationClock.CurrentProgress == 0.0)
                return fromVal; //Here it workes fine.

            if ((double)animationClock.CurrentProgress == 1.0)
                return toVal;   //It workes also here fine.

            toVal.Opacity = (double)animationClock.CurrentProgress;


            Border Bd = new Border();
            Border Bdr = new Border();

            Bd.Width = 1.0;
            Bd.Height = 1.0;

            Bd.Background = fromVal;
            Bdr.Background = toVal;

            Bd.Visibility = Visibility.Visible;
            Bdr.Visibility = Visibility.Visible;
            Bd.Child = Bdr;

            Brush VB = new VisualBrush(Bd);
            return VB; //But here it return's a transparent brush.

            //If I return the 'toVal' variable here it animates correctly the opacity.
        }
    }
}

Answer 1

The reason I need to animate a brush is to animate the brush in a material that I am using in a 3d object. I thought it would be easier to animate the brush than the material.

I have already used the method above to combinate brushes, but it didn't work here.

After thinking a little bit I decided to animate the Material and not the brush. It resulted to be easier than animating a brush.

[NOTE]
This animation class is adapted for my needs. It only animates the brush in the material. I am using this class to replace the brush of a material for an other.

[NOTE]
The 'to material' will at the end replace completely the 'from material', it will not end with a MaterialGroup.

Here is the MaterialAnimation Class for who needs it. I also have a Point3DCollectionAnimation Class. It can be used to animate 3D meshes. It's very useful. You can find it below this one.

MaterialAnimation

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Media.Animation;
using System.Windows;
using System.Windows.Media;
using System.Windows.Controls;
using System.Windows.Media.Media3D;

namespace System.Windows.Media.Animation
{
    class MaterialAnimation : AnimationTimeline
    {
                protected override Freezable CreateInstanceCore()
        {
            return new MaterialAnimation();

        }
        public override Type TargetPropertyType
        {
            get { return typeof(Material); }
        }
        static MaterialAnimation()
        {
            FromProperty = DependencyProperty.Register("From", typeof(Material),
                typeof(MaterialAnimation));

            ToProperty = DependencyProperty.Register("To", typeof(Material),
                typeof(MaterialAnimation));
        }
        public static readonly DependencyProperty FromProperty;
        public Material From
        {
            get
            {
                return (Material)GetValue(MaterialAnimation.FromProperty);
            }
            set
            {
                SetValue(MaterialAnimation.FromProperty, value);
            }
        }
        public static readonly DependencyProperty ToProperty;
        public Material To
        {
            get
            {
                return (Material)GetValue(MaterialAnimation.ToProperty);
            }
            set
            {
                SetValue(MaterialAnimation.ToProperty, value);
            }
        }
        public override object GetCurrentValue(object defaultOriginValue,
        object defaultDestinationValue, AnimationClock animationClock)
        {
            Material fromVal = ((Material)GetValue(MaterialAnimation.FromProperty)).CloneCurrentValue();
            Material toVal = ((Material)GetValue(MaterialAnimation.ToProperty)).CloneCurrentValue();

            if ((double)animationClock.CurrentProgress == 0.0)
                return fromVal; //Here it workes fine.

            if ((double)animationClock.CurrentProgress == 1.0)
                return toVal;   //It workes also here fine.            

            if (toVal.GetType() == (new DiffuseMaterial()).GetType())
                ((DiffuseMaterial)toVal).Brush.Opacity = (double)animationClock.CurrentProgress;
            else
                if (toVal.GetType() == (new SpecularMaterial()).GetType())
                    ((SpecularMaterial)toVal).Brush.Opacity = (double)animationClock.CurrentProgress;
                else
                    ((EmissiveMaterial)toVal).Brush.Opacity = (double)animationClock.CurrentProgress;


            MaterialGroup MG = new MaterialGroup();

            MG.Children.Add(fromVal);
            MG.Children.Add(toVal);            

            return MG; 
        }
    }
}

Here is the Point3DCollectionAnimation Class.

Point3DCollectionAnimation

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Media.Animation;
using System.Windows;
using System.Windows.Media.Media3D;

namespace System.Windows.Media.Animation
{
    public class Point3DCollectionAnimation : AnimationTimeline
    {
        protected override Freezable CreateInstanceCore()
        {
            return new Point3DCollectionAnimation();
        }
        public override Type TargetPropertyType
        {
            get { return typeof(Point3DCollection); }
        }
        static Point3DCollectionAnimation()
        {
            FromProperty = DependencyProperty.Register("From", typeof(Point3DCollection),
                typeof(Point3DCollectionAnimation));

            ToProperty = DependencyProperty.Register("To", typeof(Point3DCollection),
                typeof(Point3DCollectionAnimation));
        }
        public static readonly DependencyProperty FromProperty;
        public Point3DCollection From
        {
            get
            {
                return (Point3DCollection)GetValue(Point3DCollectionAnimation.FromProperty);
            }
            set
            {
                SetValue(Point3DCollectionAnimation.FromProperty, value);
            }
        }
        public static readonly DependencyProperty ToProperty;
        public Point3DCollection To
        {
            get
            {
                return (Point3DCollection)GetValue(Point3DCollectionAnimation.ToProperty);
            }
            set
            {
                SetValue(Point3DCollectionAnimation.ToProperty, value);
            }
        }
        public override object GetCurrentValue(object defaultOriginValue,
        object defaultDestinationValue, AnimationClock animationClock)
        {
            Point3DCollection fromVal = ((Point3DCollection)GetValue(Point3DCollectionAnimation.FromProperty));
            Point3DCollection toVal = ((Point3DCollection)GetValue(Point3DCollectionAnimation.ToProperty));

            Point3DCollection ret;

            int t = 0;
            if (fromVal.Count > toVal.Count)
            {
                ret = fromVal.Clone();
                foreach (Point3D tov in toVal)
                {
                    Point3D frov = fromVal[t];
                    Point3D newv = new Point3D();

                    newv.X = (double)animationClock.CurrentProgress * (tov.X - frov.X) + frov.X;
                    newv.Y = (double)animationClock.CurrentProgress * (tov.Y - frov.Y) + frov.Y;
                    newv.Z = (double)animationClock.CurrentProgress * (tov.Z - frov.Z) + frov.Z;
                    ret[t] = newv;
                    t++;
                }
            }
            else
            {
                ret = toVal.Clone();
                foreach (Point3D frov in fromVal)
                {
                    Point3D tov = toVal[t];
                    Point3D newv = new Point3D();

                    newv.X = (double)animationClock.CurrentProgress * (tov.X - frov.X) + frov.X;
                    newv.Y = (double)animationClock.CurrentProgress * (tov.Y - frov.Y) + frov.Y;
                    newv.Z = (double)animationClock.CurrentProgress * (tov.Z - frov.Z) + frov.Z;
                    ret[t] = newv;
                    t++;
                }
            }

            return ret;
        }
    }
}

I hope these classes are usefull for who needs them. I searched for them allot on the internet, but didn't find them. I'm sure that there are more people who needs these classes.

Please leave comments.

Answer 2

I discovered the problem. Visual Brushes are not freezable. To the code to work I will need to find a way to freeze the brush.

Answer 3

Aaron, I have used your BrushAnimation class as shown above, and it works for my specific needs. However, I noticed that StackOverflow operates under the Creative Commons licence. Thus I technically couldn't use that class in my commercial application (which I don't want to be under the Creative Commons licence) without your permission. Are you willing to give me permission? I can still credit your work.

I couldn't find any other way to contact you about this, since I can't make comments yet.

Answer 4

The above approach should work as long as you have transparent pixels in the front brush. If not the front brush would just overlay the back brush. You should provide a more complete example to see what is actually going on.

Answer 5

You can use a visualbrush to achieve that

<Grid.Background>
       <VisualBrush>
                <VisualBrush.Visual>
                    <Grid 
                        Width="{Binding Path=ActualWidth, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type FrameworkElement}}, Mode=OneWay}" 
                        Height="{Binding Path=ActualHeight, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type FrameworkElement}}, Mode=OneWay}">

                        <Rectangle Fill="Blue" />
                        <Image Source="your image path" Stretch="Uniform" />

                    </Grid>
                </VisualBrush.Visual>
            </VisualBrush>
        </Grid.Background>