/// <summary>
/// fit image 100% considering margin
/// </summary>
public static Picture ImageFit(this DocX docx, string pathfilename, double factor = 1.0)
{
var page_width_in = docx.PointsToMeasure((int)docx.PageWidth).Value;
var page_width_avail_in = page_width_in -
docx.PointsToMeasure((int)docx.MarginLeft).Value -
docx.PointsToMeasure((int)docx.MarginRight).Value;
factor = factor * (page_width_avail_in / page_width_in);
var img = docx.AddImage(pathfilename);
var res = img.CreatePicture();
var ratio_w_h = (double)res.Width / res.Height;
res.SetSizeInches(page_width_avail_in, page_width_avail_in / ratio_w_h);
return(res);
}