What I want to do is either:
Or if there is other way to achieve this?
Yes, you can do this by loading the bitmap using SKBitmap.Decode()... you can pass the image as a byte, stream or a string (among other options) to this method. Once you have your SKBitmap, then you will be able to draw on it.
I had a sample that did just that: https://github.com/mono/SkiaSharp/blob/master/samples/Gallery/Shared/Samples/BitmapAnnotationSample.cs
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