In Silverlight 4: how to set the Opacity of a Stroke programmatically?

Question

I want to set the opacity of a Stroke which is obtained from a user drawing on the screen. I can get the drawing, size, outline of the stroke to set but not the Opacity of it.

This is my code

StylusPointCollection spTemp = e.StylusDevice.GetStylusPoints(MyIP);
        tempStroke.StylusPoints.Add(spTemp);

        tempStroke.DrawingAttributes.Color = Colors.Red;
        tempStroke.DrawingAttributes.OutlineColor = Colors.Black;

        tempStroke.DrawingAttributes.Width = BrushSize.Value;
        tempStroke.DrawingAttributes.Height = BrushSize.Value;

        MyIP.Strokes.Add(tempStroke);

Any help is appreciated

Simple Code

Answer 1

Set the alpha value on the color. eg for an opacity of +-0.5 and color red:

tempStroke.DrawingAttributes.Color = Colors.FromArgb(125,255,0,0);

Answer 2

I think your going to have to set the Alpha on the color. for example:

//the first 00 would be your alpha channel, then red, then green, then blue
tempStroke.DrawingAttributes.Color = Colors.FromArgb(0x00,0xFF,0x00,0x00);

Answer 3

You can set the Color.A property to a value from 0 to 255 or set the Color.ScA property to a decimal value from 0 to 1. The two properties are kept in sync, so if you change one, expect the other to update to an equivalent value.

http://msdn.microsoft.com/en-us/library/system.windows.media.color.aspx