Graphics g = Graphics.FromImage(image);

                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;//设置图片质量

                g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;

                g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;

                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;