The ImageSource property of the Button class is of ImageSource type, whose value can be set to that of a string representing the path of an image either via assigning the string to the property or using the ImageSource.FromFile() method. As the ImageSource type cannot be used with SKBitmap images, the image represented by the SKBitmap object can be saved to the disk (preferably in the application cache) and the path to the saved image can be used to initialize the concerned ImageSource object.
SKBitmap bitmap;
SKImage image = SKImage.FromBitmap(bitmap);
SKData encodedData = image.Encode(SKEncodedImageFormat.Png, 100);
string imagePath = Path.Combine(FileSystem.CacheDirectory, "image.png");
bitmapImageStream = File.Open(imagePath,
FileMode.Create,
FileAccess.Write,
FileShare.None);
encodedData.SaveTo(bitmapImageStream);
bitmapImageStream.Flush(true);
bitmapImageStream.Dispose();
ImageSource imgSrc;
imgSrc = ImageSource.FromFile(imagePath);
// or imgSrc = imagePath;