任意角度旋转图片

       ///

        /// 任意角度旋转

        ///

        /// 原始图Bitmap

        /// 旋转角度

        /// 背景色

        /// 输出Bitmap

        public static Bitmap KiRotate(Bitmap bmp, float angle, Color bkColor)

        {

            int w = bmp.Width + 2;

            int h = bmp.Height + 2;

            PixelFormat pf;

            if (bkColor == Color.Transparent)

            {

                pf = PixelFormat.Format32bppArgb;

            }

            else

            {

                pf = bmp.PixelFormat;

            }

            Bitmap tmp = new Bitmap(w, h, pf);

            Graphics g = Graphics.FromImage(tmp);

            g.Clear(bkColor);

            g.DrawImageUnscaled(bmp, 1, 1);

            g.Dispose();

            GraphicsPath path = new GraphicsPath();

            path.AddRectangle(new RectangleF(0f, 0f, w, h));

            Matrix mtrx = new Matrix();

            mtrx.Rotate(angle);

            RectangleF rct = path.GetBounds(mtrx);

            Bitmap dst = new Bitmap((int)rct.Width, (int)rct.Height, pf);

            g = Graphics.FromImage(dst);

            g.Clear(bkColor);

            g.TranslateTransform(-rct.X, -rct.Y);

            g.RotateTransform(angle);

            g.InterpolationMode = InterpolationMode.HighQualityBilinear;

            g.DrawImageUnscaled(tmp, 0, 0);

            g.Dispose();

            tmp.Dispose();

            return dst;

        }