客户端上传图片到服务器怎么实现自动压缩图片的大小那？？

Question

菜鸟请教。。怎么实现压缩图片大小的功能？

Answer 1

将原图上传到服务器后，用draw把原图重绘。
  public Bitmap MakeThumb(System.Drawing.Image OImage, int k, int tw, int th)
        {
            int ow = OImage.Width;
            int oh = OImage.Height;
            int a = 0;
            int b = 0;
            int c = ow;
            int d = oh;
            int nw = tw;
            int nh = th;
            double x1 = Convert.ToDouble(Convert.ToDouble(ow) / Convert.ToDouble(tw));
            double x2 = Convert.ToDouble(Convert.ToDouble(oh) / Convert.ToDouble(th));
            switch (k)
            {
                case 1://取中心部分
                    if (x1 > x2)
                    {
                        b = 0;
                        d = oh;
                        c = Convert.ToInt32(oh * Convert.ToDouble(Convert.ToDouble(tw) / Convert.ToDouble(th)));
                        a = (ow - c) / 2;
                    }
                    else
                    {
                        a = 0;
                        c = ow;
                        d = Convert.ToInt32(ow * Convert.ToDouble(Convert.ToDouble(th) / Convert.ToDouble(tw)));
                        b = (oh - d) / 2;
                    }
                    break;
                case 2://强制宽度符合缩略图
                    nh = Convert.ToInt32(oh * Convert.ToDouble(Convert.ToDouble(tw) / Convert.ToDouble(ow)));
                    break;
                case 3://强制高度符合缩略图
                    nw = Convert.ToInt32(ow * Convert.ToDouble(Convert.ToDouble(th) / Convert.ToDouble(oh)));
                    break;
                case 4://宽度大于缩略图宽度时缩略，否则原图重绘
                    if (ow > tw)
                    {
                        nh = Convert.ToInt32(oh * Convert.ToDouble(Convert.ToDouble(tw) / Convert.ToDouble(ow)));
                    }
                    else
                    {
                        nw = ow;
                        nh = oh;
                    }
                    break;
                case 5://高度大于缩略图高度时缩略，否则原图重绘                    if (oh > th)
                    {
                        nw = Convert.ToInt32(ow * Convert.ToDouble(Convert.ToDouble(th) / Convert.ToDouble(oh)));
                    }
                    else
                    {
                        nw = ow;
                        nh = oh;
                    }
                    break;
                case 6://原图重绘
                    nw = ow;
                    nh = oh;
                    break;
                case 7://宽度大于缩略图宽度时缩略，否则原图重绘                    if ((ow > tw) || (oh > th))
                    {
                        if (x1 > x2)
                        {
                            nh = Convert.ToInt32(oh * Convert.ToDouble(Convert.ToDouble(tw) / Convert.ToDouble(ow)));
                        }
                        else
                        {
                            nw = Convert.ToInt32(ow * Convert.ToDouble(Convert.ToDouble(th) / Convert.ToDouble(oh)));
                        }
                    }
                    else
                    {
                        nw = ow;
                        nh = oh;
                    }                  
                    break;
            }//k值不在范围内时，强制缩略成原图，变形。            Bitmap bitmap = new System.Drawing.Bitmap(nw, nh, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
         
            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;            g.Clear(System.Drawing.Color.White);
            g.DrawImage(OImage, new System.Drawing.Rectangle(0, 0, nw, nh), new System.Drawing.Rectangle(a, b, c, d), System.Drawing.GraphicsUnit.Pixel);//绘图
            g.Dispose();
            return bitmap;
        }

Answer 2

服务器端读取图片，用Graphic.DrawImage按照比例缩放，绘制好了再存回去。