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.
Related
I am not a real designer and I would like to know if anyone have an idea how can I build the following visual :
The idea is to get 2 rings where inside I will draw secific number of pie represented as "Interactive shape or button". Base on the number of shape, they should cover the whole circle.
In addition to that, I need to be able to interact with each pie shape, and inside and oustide edge of those shape should be a perfect arc based on the circle diameter.
As I am not a perfect designer, how can I represent this visual ?
I was thinking of using a custom panel but then how to draw each panel shape in order that they gets perfect inside and ouside arc and offer interactivity with each of them ?
Thanks for your help
I would appreciate samples as well
Theres actually a Silverlight tutorial on making something exactly like this.
If you didnt want to use that, you could always do it in javascript. Here's an example using Rapheal js
I would recommend looking into WPF Geometry and how you can create custom controls (such as the Circular Gauge Custom Control over on CodeProject) using said Geometry.
I've never created a control quite like what your suggesting, but I would image you would define some form of area that can contain children and style it so that it forms the circular shape you want. Then, adding interactive regions should be as simple as adding controls to standard containers.
Here's a link to a "generic radial panel that can be used to host any items" which subclasses Panel.
We have a control which we do our own custom drawing in OnRender. However, we would like to use a PNG with transparency as sort of a stencil for various drawing 'passes' if you will.
Now we already know that we can simply use a PNG in an ImageBrush and set it as the control's OpacityMask, but we actually want to do several drawing passes with several different stencils. If we wanted to go the OpacityMask route, we'd have to create separate controls, separate ImageMasks, then stack them all up on top of each other which also clutters up your visual tree.
We don't want to do that. We want to do all of the drawing in the OnRender override of a single Control subclass. We just want those draw calls to be masked out by an image. We then want to repeat that over and over until our drawing is done.
Any way this can be done?
HA! Found it! Odd that the S/O community has been so quiet on this one, but for those looking for it, it's called DrawingContext.PushOpacityMask (and the corresponding 'Pop()') and does exactly what you think it does... it pushes an opacity mask (via a brush) onto the DC and all subsequent drawing is relative to the brush's opacity values.
You can also layer 'masks' for some pretty cool effects too. They are additive, not just the last one set.
I'm pretty sure the built-in OpacityMask is just used with this function in the OnRender call. What this means is you can still use the OpacityMask (provided you push that on first) then your own mask(s) for your own drawing calls. Pretty neat stuff!
Hope this helps others who were looking for this.
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...
I want to put an image on a button, but I want part of the image to be transparent. How do I do this?
Try the Image.OpacityMask property. You can give it a brush that specifies the region you want to be transparent.
EDIT: From MSDN:
There is no direct support for
color-keying a bitmap in WPF.
However, it is fairly easy to
implement on your own. Dwayne has
implemented a ColorKeyBitmap on his
blog:
http://blogs.msdn.com/dwayneneed/archive/2008/06/20/implementing-a-custom-bitmapsource.aspx
I believe it links to the code on
Codeplex as well. You could also
accomplish this simply by reading your
bitmap into system memory, iterating
through all the pixels and setting
their values yourself, and
constructing a new bitmap out of that
array.
Use a paint program (I use Paint.Net) to change the area you want transparent to an alha=0 color. Then save the image (mine was JPG) as a PNG. Seemed to work fine for me in the WPF Image control.