IOS绘制一个简单的图像变得模糊使用Xamarin C#

我正在开发Xamarin,并希望在其中绘制一个带有“CIRCLE”文本的简单圆圈,并在UI ImageView中显示该图像.问题是圆圈和文字显得非常模糊.我已经阅读了一些有关子像素的内容,但我认为这不是我的问题.

这是模糊的图像和代码,希望有人有一些想法:)

UIGraphics.beginImageContext (new SizeF(150,150));
var context = UIGraphics.GetCurrentContext ();

var content = "CIRCLE";
var font = UIFont.SystemFontOfSize (16);

const float width = 150;
const float height = 150;

context.SetFillColorWithColor (UIColor.Red.CGColor);
context.FillEllipseInRect (new RectangleF (0,width,height));

var contentString = new NSString (content);
var contentSize = contentString.StringSize (font);

var rect = new RectangleF (0,((height - contentSize.Height) / 2) + 0,contentSize.Height);

context.SetFillColorWithColor (UIColor.White.CGColor);
new NSString (content).DrawString (rect,font,UILineBreakmode.WordWrap,UITextAlignment.Center);

var image = UIGraphics.GetImageFromCurrentImageContext ();
imageView.Image = image;

UIGraphics.beginImageContextWithOptions (size,false,0);