RoundCornersProcessor for ImageSharp

RoundCornersProcessor.cs

using SixLabors.ImageSharp;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing;
using SixLabors.Primitives;
using SixLabors.Shapes;

namespace EQL.ImageSharp
{
    public static class RoundCornersProcessor
    {
        public static IImageProcessingContext ApplyRoundedCorners(this IImageProcessingContext ctx, float cornerPercentX, float cornerPercentY)
        {
            Size size = ctx.GetCurrentSize();
            IPathCollection corners = BuildCorners(size.Width, size.Height, cornerPercentX, cornerPercentY);
            var graphicOptions = new GraphicsOptions(true)
            {
                AlphaCompositionMode = PixelAlphaCompositionMode.DestOut
            };
            return ctx.Fill(graphicOptions, Rgba32.Black, corners);
        }

        private static IPathCollection BuildCorners(int imageWidth, int imageHeight, float cornerPercentX, float cornerPercentY)
        {
            var cornerRadiusX = imageWidth * (cornerPercentX / 100.0f);
            var cornerRadiusY = imageHeight * (cornerPercentY / 100.0f);

            var rightOffset = imageWidth - cornerRadiusX;
            var bottomOffset = imageHeight - cornerRadiusY;

            var rect = new RectangularPolygon(0, 0, cornerRadiusX, cornerRadiusY);
            IPath cornerTopLeft = rect.Clip(new EllipsePolygon(cornerRadiusX, cornerRadiusY, cornerRadiusX * 2, cornerRadiusY * 2));
            IPath cornerTopRight = rect.Clip(new EllipsePolygon(0, cornerRadiusY, cornerRadiusX * 2, cornerRadiusY * 2)).Translate(rightOffset, 0);
            IPath cornerBottomLeft = rect.Clip(new EllipsePolygon(cornerRadiusX, 0, cornerRadiusX * 2, cornerRadiusY * 2)).Translate(0, bottomOffset);
            IPath cornerBottomRight = rect.Clip(new EllipsePolygon(0, 0, cornerRadiusX * 2, cornerRadiusY * 2)).Translate(rightOffset, bottomOffset);
            return new PathCollection(cornerTopLeft, cornerTopRight, cornerBottomLeft, cornerBottomRight);
        }
    }
}