I've seen examples in silverlight where the achieve a effect using 1 of 2 ways:
Two image objects, both
displaying the same image, but the
bottom one rotating it 180 degrees
and applying a gradient image
opacity
A MediaElement object and a VideoBrush element.
I have a series of path objects, rectanges, etc which I would like to apply a reflection affect to. Is there a more elegant solution other than copying my objects manually and rotating them? Unfortunately the VideoBrush object only works on MediaElement objects, but is there something else I can use?
Not in Silverlight, in WPF you have a VisualBrush which can help with this but Silverlight doesn't have one in version 2. Just to be clear though, it's not a rotation it's a negative ScaleY on a ScaleTransform. The easiest thing is to put everything into a UserControl and then use two UserControls with one having a ScaleTransform and an OpacityMask on it.
For a good example, please see the following blog post from Mike Snow.
http://silverlight.net/blogs/msnow/archive/2008/09/04/silverlight-tip-of-the-day-36-how-to-create-reflections-and-shadows-for-images-and-text.aspx
Related
I'm currently looking to achieve a gradient effect a bit like the rectangle in http://pjnicholson.com/Fireworks/fillgradients.htm
If I compromise a little I can get close to this using RadialGradientBrush... but is there any (not too painful) way to achieve the rectangular effect?
Use an ImageBrush instead and use this image (or a similar image generated using some image editor) for the background of your rectangle.
One solution a colleague and I came with was to derive a new Panel that used a WriteableBitmap as the source for its background.
The panel will give you the dimensions you need to make your WriteableBitmap. Using whatever algorithm you want you can fill it appropriately. In our case, we needed a radial or cone gradient, but the same concept applies.
Additionally, you can create several properties on your new control to specify the colors for the gradient. We adapted a LinearGradientBrush for our needs, but if you're working on just two colors, simple properties may suffice.
I don't have the code handy but will try to find it and post an update later. But the above should get you going.
I am developing a Maps like application using WPF. I have ~10,000 PathGeometry, Shapes added to the canvas. I have added ScaleTransform and TranslateTransform for zooming and panning controls.
The problem I'm facing is, when I zoom or pan, there is slight lag. Is there a way to organize the data so that I handle only the Shapes that are visible?
Any hints on making it more efficient will be helpful and appreciated.
What kind f stuff are you putting on the canvas? If using pathGeometry, are you enclosing them in Path class? If so, Path has FrameworkElement in its superclass hierarchy, which is responsible for massive performance loss.
Take a look at my question here. Although it is about Shape class, but the reason of performance degradation is the same, FrameworkElement.
If you are doing so, the solution is to use PathGeometry instead, and enclose it in DrawingContext of a DrawingVisual using DrawingContext.DrawGeometry() method.
Here are some links that should help.
Path Geometry
DrawingContext.DrawGeometry()
Optimizing Performance: 2D Graphics and Imaging
And draw the shapes yourself, using combination of lines, and other things provided by classes derived from Geometry class (ArcGeometry, PathGeometry etc).
This should help.
If you want the ultimate in performance for immediate drawing in WPF, then check out WriteableBitmapEx. This is an excellent open source library, which I recently contributed to. it provides GDI-like drawing capabilities on WriteableBitmap and is compatible with Windows Phone, WPF and Silverlight. The API is simple, you get blitting, polygons, lines and simple shapes etc... You won't get datatemplates and gradient brushes however.
Before drawing a shape on a canvas I have a preview that displays how the shape will look. I can adjust the opacity and then draw the shape. I may then wish to draw a second shape with a different opacity. My problem is that altering the opacity of the preview also alters the opacity of the shape that I have already drawn.
This has led me to believe that I need to create a copy of the brush used for the preview each time before drawing the shape.
There are various different brushes and for example, the gradient brushes require making a copy of the not just the gradient stop collection, but a new gradient stop for each gradient stop in the to-be-copied collection.
Am I down the right track here or should I be doing something else? Should I be copying or cloning? Would an extension method be the best way to go? Thoughts please.
What you need is cloning, it would be easy in wpf with XamlWriter/Reader, unfortunately you cannot do it in Silverlight. An extension method on Brush that makes a deep copy would work fine in your case though. You will have to handle the different brush type separately but it should not be an issue as there aren't that many.
The System.Drawing.Graphics class has a property CompositionMode with two options: SourceOver (which, based on the alpha component, blends whatever is drawn with the background already existing) or SourceCopy which simply overwrites the background with whatever is being drawn.
Does something similar exist in WPF?
In WPF when i draw a PolyLine for example on top of another the new PolyLine always alphablends with the background. I think that is independent of the container being used. I am using a Canvas but could not find a blend mode property anywhere. What I want to do is what the SourceCopy compositionmode mentioned above does. I.e. the new PolyLine should simply overwrite whatever is already on the Canvas.
Is there a simple way to do that, short of using pixel shaders (which - as far as I understand - wouldn't work anyways because I don't have access to the Canvas backbuffer).
I am not stuck with a Canvas and would be happy to use any container that supports overwrite mode.
I currently have a solution based on a WriteableBitmap for which I obtain a System.Drawing.Graphics context and then manipulate the CompositionMode. It works but since my window is fullscreen that solution has serious performance impacts.
Clarification and example:
The WPF window is fully transparent and so is the Canvas (back ground color(0,0,0,0)). Now I draw a PolyLine with a Color.FromArgb(128,128,0,0). I now have a semi-transparent red polyline. Next I draw the same PolyLine with Color.FromArgb(0,0,0,0). The result is the same as before because of the alpha blending taking place. What I want, however, is that the red polyline is erased with the second polyline (which is exactly what the SourceCopy mode in the Graphics class does.
I think all you need to do is make sure that the brushes used to fill/stroke the PolyLine have fully opaque alpha values (i.e. 255). Then the background shouldn't be blended into it.
You could apply a Clipping Mask, this way you can provide the path to clip over the elements that are below it, but it might be tough to maintain after a lot elements are required to be clipped...
is this possible?
Once you have got the video displayed (see your previous question), set the display element's LayoutTransform or RenderTransform to a suitable RotateTransform. If you wish to flip the video instead, use a ScaleTransform with a negative scale. If you wish to do both, use a TransformGroup containing both a ScaleTransform and a RotateTransform.
Check out the WPF MediaKit, which has code for webcams. You can use standard WPF transforms to do your rotating.