Mask image in Xamarin Forms Android and iOS - image

Question

I want to mask an image like the sample below:
I tried using the FFImageLoading Transformation, but I couldn't get the triangle shape that is in the image shown.
Also, I cannot do the trick of putting the background white, because I want to achieve this final result:
Is there any way to get the pixels of the triangle shape that are not in alpha, and convert them to the squared image pixels?
I tried this code from SkiaSharp changing the values of the SKPath, but this complicates more my problem because it is not an image, is a canvas:
public class MonkeyThroughKeyholePage : ContentPage
{
SKBitmap bitmap;
SKPath keyholePath = SKPath.ParseSvgPathData(
"M 200 130 L 250 300 L 250 300 L 300 130 A 70 70 20 1 20 300 130 Z");
public MonkeyThroughKeyholePage()
{
Title = "Monkey through Keyhole";
SKCanvasView canvasView = new SKCanvasView();
canvasView.PaintSurface += OnCanvasViewPaintSurface;
Content = canvasView;
string resourceID = "SkiaSharpFormsDemos.Media.SeatedMonkey.jpg";
Assembly assembly = GetType().GetTypeInfo().Assembly;
using (Stream stream = assembly.GetManifestResourceStream(resourceID))
using (SKManagedStream skStream = new SKManagedStream(stream))
{
bitmap = SKBitmap.Decode(skStream);
}
}
void OnCanvasViewPaintSurface(object sender, SKPaintSurfaceEventArgs args)
{
SKImageInfo info = args.Info;
SKSurface surface = args.Surface;
SKCanvas canvas = surface.Canvas;
canvas.Clear();
// Set transform to center and enlarge clip path to window height
SKRect bounds;
keyholePath.GetTightBounds(out bounds);
canvas.Translate(info.Width / 2, info.Height / 2);
canvas.Scale(0.98f * info.Height / bounds.Height);
canvas.Translate(-bounds.MidX, -bounds.MidY);
// canvas.RotateDegrees(15f);
// Set the clip path
canvas.ClipPath(keyholePath);
// Reset transforms
canvas.ResetMatrix();
canvas.DrawBitmap(bitmap,
new SKRect((info.Width - info.Height) / 2, 0,
(info.Width + info.Height) / 2, info.Height));
}
}