先看效果

平移

旋转

 缩放

对应方法 

平移

        /// <summary>
        /// 
        /// </summary>
        /// <param name="bmp">原始图像</param>
        /// <param name="x">横向平移距离(像素)</param>
        /// <param name="y">纵向平移距离(像素)</param>
        /// <param name="bkColor"></param>
        /// <returns></returns>
        public static Bitmap Move(Bitmap bmp, int x, int y, Color bkColor)
        {
            Bitmap backBitmap = new Bitmap(bmp.Width + x, bmp.Height + y);
            Graphics g = Graphics.FromImage(backBitmap);
            g.Clear(bkColor);
            g.DrawImageUnscaled(bmp, x, y);
            g.Dispose();
            return backBitmap;
        }

 旋转

        /// <summary>
        /// 旋转图像
        /// </summary>
        /// <param name="bmp">原始图像</param>
        /// <param name="angle">旋转角度(角度制)</param>
        /// <param name="backColor">背景色</param>
        /// <returns>输出Bitmap</returns>
        public static Bitmap Rotate(Bitmap bmp, float angle, Color backColor)
        {
            int w = bmp.Width + 2;
            int h = bmp.Height + 2;

            PixelFormat pf;

            if (backColor == Color.Transparent)
            {
                pf = PixelFormat.Format32bppArgb;
            }
            else
            {
                pf = bmp.PixelFormat;
            }

            Bitmap tmp = new Bitmap(w, h, pf);
            Graphics g = Graphics.FromImage(tmp);
            g.Clear(backColor);
            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(backColor);
            g.TranslateTransform(-rct.X, -rct.Y);
            g.RotateTransform(angle);
            g.InterpolationMode = InterpolationMode.HighQualityBilinear;
            g.DrawImageUnscaled(tmp, 0, 0);
            g.Dispose();

            tmp.Dispose();

            return dst;
        }

缩放

        /// <summary>
        /// 缩放图像
        /// </summary>
        /// <param name="bitmap">原始图像</param>
        /// <param name="scaleX">横向缩放(比例)</param>
        /// <param name="scaleY">纵向缩放(比例)</param>
        /// <returns></returns>
        public static Bitmap Scale(Bitmap bitmap, float scaleX, float scaleY)
        {
            if (scaleX < 0) bitmap.RotateFlip(RotateFlipType.RotateNoneFlipX);
            if (scaleY < 0) bitmap.RotateFlip(RotateFlipType.RotateNoneFlipY);
            return new Bitmap(bitmap, new Size((int)Math.Abs(bitmap.Width * scaleX), (int)Math.Abs(bitmap.Height * scaleY)));
        }

参考：https://www.cnblogs.com/hetonghai/p/1211394