Drawing line on a UIImage NOT UIImageView - Xamarin iOS - ios

Question

Hello I currently have this method which draws line on an UIImageView.
However I am trying to make it compatible with a UIImage and have not had any luck. This example here works beautifully for text but not great for lines.
DrawOnUIImageView.cs
private void Draw(Face face, UIImageView imageView)
{
CAShapeLayer boundingBoxLayer = new CAShapeLayer();
boundingBoxLayer.Frame = face.rect;
boundingBoxLayer.FillColor = null;
boundingBoxLayer.StrokeColor = UIColor.Red.CGColor;
imageView.Layer.AddSublayer(boundingBoxLayer);
CAShapeLayer secondBoxLayer = new CAShapeLayer();
secondBoxLayer.FillColor = null;
secondBoxLayer.StrokeColor = UIColor.Green.CGColor;
boundingBoxLayer.AddSublayer(secondBoxLayer);
var path = new CGPath();
List<LandmarkLine> lines = new List<LandmarkLine>();
foreach (var landmark in face.landmarks)
{
List<CGPoint> addTo = new List<CGPoint>();
foreach (var point in landmark.points)
{
addTo.Add(new CGPoint((point.X * face.rect.Width), (1 - point.Y) * face.rect.Height));
}
CGPath outline = new CGPath();
outline.AddLines(addTo.ToArray());
outline.CloseSubpath();
path.AddPath(outline);
}
secondBoxLayer.Path = path;
//imageView.Layer.AddSublayer(outline);
}
Any advice on this would be great. Thanks

Answer 1

You can draw a line on your image like this:
private UIImage drawLineOnImage(UIImage img)
{
//UIImage orgImage = <YOUR IMAGE>
UIGraphics.BeginImageContext(orgImage.Size);
// 1: Draw the original image as the background
orgImage.Draw(new RectangleF(0,0,(float)orgImage.Size.Width,(float)orgImage.Size.Height));
// 2: Draw the line on the image
CGContext context = UIGraphics.GetCurrentContext();
context.SetLineWidth(1.0f);
context.MoveTo(0, 80);
context.AddLineToPoint(orgImage.Size.Width, 80);
context.SetStrokeColor(UIColor.Blue.CGColor);
context.StrokePath();
// Create new image
UIImage image = UIGraphics.GetImageFromCurrentImageContext();
// Tidy up
UIGraphics.EndImageContext();
return image;
}
This code will create a new image as the original image size, then draw a copy of the original image onto the new image and draw a line on the new image.