C# Windows Phone - Creating a round mask

Question

I need to mask dynamically created images, so that they will be shown as circles. Pictures can be square, but are usually rectangles... so the circle that will be shown can be taken from the center of it...so the shown circle must be inscribed in the picture and centered in the center of it.

This is the code I'm using right now:

//Setting up the image
Image image = new Image();
image.Height = 70;
image.Width = 70;
BitmapImage bitmapImage = new BitmapImage();
bitmapImage.UriSource = new Uri("http://url-of-the-image", UriKind.Absolute);
image.CacheMode = new BitmapCache();
image.Source = bitmapImage;
image.Stretch = Stretch.UniformToFill;
image.VerticalAlignment = System.Windows.VerticalAlignment.Center;

//Setting up the mask
RadialGradientBrush opacityMask = new RadialGradientBrush();
GradientStop gs1 = new GradientStop();
GradientStop gs2 = new GradientStop();
GradientStop gs3 = new GradientStop();
gs1.Color = Color.FromArgb(255, 0, 0, 0);
gs1.Offset = 0.0;
gs2.Color = Color.FromArgb(255, 0, 0, 0);
gs2.Offset = 0.999;
gs3.Color = Color.FromArgb(0, 0, 0, 0);
gs3.Offset = 1.0;
opacityMask.GradientStops.Add(gs1);
opacityMask.GradientStops.Add(gs2);
opacityMask.GradientStops.Add(gs3);
image.OpacityMask = opacityMask;

//Showing the image
panel.Children.Add(image);

This all works fine, but when the pictures are rectangular and not square, this creates an ellipse instead of a circle... any idea on how can I force it to create a circle?

I also tried to specify some more parameters, but doesn't seem to help:

opacityMask.Center = new Point(0.5, 0.5);
opacityMask.RadiusX = 0.5;
opacityMask.RadiusY = 0.5;

Answer 1

Okay, today i tried again to fix this, and i came out with a solution. It's not the best, more clean solution ever...but works :)

I basically wrapped the picture (not masked) into a StackPanel and then applied the mask to the StackPanel instead ;)

This is how it looks like (the only lines that change from the original are the the last few ones):

//Setting up the image
Image image = new Image();
image.Height = 70;
image.Width = 70;
BitmapImage bitmapImage = new BitmapImage();
bitmapImage.UriSource = new Uri("http://url-of-the-image", UriKind.Absolute);
image.CacheMode = new BitmapCache();
image.Source = bitmapImage;
image.Stretch = Stretch.UniformToFill;
image.VerticalAlignment = System.Windows.VerticalAlignment.Center;

//Setting up the mask
RadialGradientBrush opacityMask = new RadialGradientBrush();
GradientStop gs1 = new GradientStop();
GradientStop gs2 = new GradientStop();
GradientStop gs3 = new GradientStop();
gs1.Color = Color.FromArgb(255, 0, 0, 0);
gs1.Offset = 0.0;
gs2.Color = Color.FromArgb(255, 0, 0, 0);
gs2.Offset = 0.999;
gs3.Color = Color.FromArgb(0, 0, 0, 0);
gs3.Offset = 1.0;
opacityMask.GradientStops.Add(gs1);
opacityMask.GradientStops.Add(gs2);
opacityMask.GradientStops.Add(gs3);

//Setting up the StackPanel
StackPanel sp = new StackPanel();
sp.OpacityMask = opacityMask;

//Showing the image
sp.Children.Add(image);
panel.Children.Add(sp);