/// <summary>
/// Renders the passed in images over top the source image, masking with elliptical or rectangular opacity mask as specified, returns an image of this.
/// </summary>
/// <param name="sourceImage">Image to be overlaid</param>
/// <param name="overlayPositions">Positions to draw facesToOverlay on sourceImage</param>
/// <param name="facesToOverlay">Images to be overlaid on sourceimage</param>
/// <param name="howToClip">Rectangular or elliptical clipping</param>
/// <returns></returns>
private static BitmapSource _AddOverlay(BitmapSource sourceImage, IList <Rect> overlayPositions, IList <ImageSource> overlayImages, ClipAlgorithm howToClip)
{
Verify.IsNotNull(sourceImage, "sourceImage");
Verify.IsNotNull(overlayPositions, "overlayPositions");
Verify.IsNotNull(overlayImages, "facesToOverlay");
var imageCompositor = new Canvas
{
Width = sourceImage.PixelWidth,
Height = sourceImage.PixelHeight,
};
imageCompositor.Children.Add(new Image {
Source = sourceImage
});
// Note that the overlay rects and images may not match in length.
// The user may not have enough friends to fill in the splash screen. This is okay.
foreach (var pair in overlayPositions.Zip(overlayImages, (rect, img) => new { Img = img, Rect = rect }))
{
imageCompositor.Children.Add(_GetCanvasOverlay(pair.Img, pair.Rect, howToClip));
}
return(Utility.GenerateBitmapSource(imageCompositor, imageCompositor.Width, imageCompositor.Height, true));
}
// Creates an element with Canvas attached DPs and appropriate masking if specified.
private static UIElement _GetCanvasOverlay(ImageSource overlaySource, Rect overlayPosition, ClipAlgorithm howToClip)
{
Brush opacityBrush = null;
switch (howToClip)
{
case ClipAlgorithm.Elliptical:
double dimensionDelta = overlayPosition.Height - overlayPosition.Width;
opacityBrush = new DrawingBrush
{
Drawing = new GeometryDrawing
{
Geometry = new EllipseGeometry(overlayPosition),
Brush = new RadialGradientBrush
{
GradientOrigin = new Point(0.5, 0.5),
Center = new Point(0.5, 0.5),
// Since we subtracted Height From Width above (arbitrary) to normalize radii for
// the gradient, subtract for Width and add for Height (I can show this on paper but this "works" for stretching radius.
RadiusX = 0.5 - (0.5 * (dimensionDelta / overlayPosition.Height)),
RadiusY = 0.5 + (0.5 * (dimensionDelta / overlayPosition.Width)),
GradientStops =
{
new GradientStop(Colors.White, 0.0),
new GradientStop(Colors.White, 0.85),
new GradientStop(Colors.Transparent, 1.0),
},
},
}
};
break;
case ClipAlgorithm.Rectangular:
// TODO: Do we care to do any gradient opacity masking here?
// Doesnt't need to be answered until we have a splash screen w/ rectangular overlays.
break;
}
var rect = new Rectangle
{
Width = overlayPosition.Width,
Height = overlayPosition.Height,
Fill = new ImageBrush
{
ImageSource = overlaySource,
Stretch = Stretch.UniformToFill,
AlignmentX = AlignmentX.Center,
AlignmentY = AlignmentY.Center
},
OpacityMask = opacityBrush,
};
Canvas.SetLeft(rect, overlayPosition.Left);
Canvas.SetTop(rect, overlayPosition.Top);
return(rect);
}
