How to prevent graphical stutter when scrolling a large zoomed out picture

Question

I have a large TIFF picture (5.9 MB, 13k X 16k resolution) that the user loads into a scrollable panel that he then can zoom in/out of, scroll and mark points, regions etc. on.<

Answer 1

Is not tested, but should give an idea.

Bitmap _cached = null;

override void OnPaint(PaintEventArgs e)
{
    if(_cached == null)
    {
        _cached = new Bitmap(this.ClientSize.Width, this.ClientSize.Height);
        using(var graphics = Graphics.FromImage(_cached)
        {
             // draw into this graphics once -> it will be cached in _cached bitmap
        }
    }
    e.Graphics.DrawImage(_cached, Point.Empty);
}

// call this if _zoom or ClientSize is changed
void ResetCache()
{
    _cache = null;
    this.Invalidate(); // mandatory for _zoom change
}

Also, I don't know how to do you present your zoomed-in picture, but usually there is an offset so that you can move (pan) image.