产生高质量成比例缩略图

 不多说了,大家看代码,生成的缩略图有超出范围的时候,但是在限制范围长和宽为1:1时肯定在范围之内.

private void Get_Image(string imgpath,string thetype,int limit_width,int limit_height) //图片路径,图片形式,范围宽,范围长
        ...{
            System.Drawing.Image originalImage = System.Drawing.Image.FromFile(Server.MapPath("temp")+"/"+imgpath);
            int pic_width = originalImage.Width;
            int pic_height = originalImage.Height;
            int towidth = 0;
            int toheight = 0;
            if(pic_width<=limit_width&&pic_height<=limit_height)
            ...{
                towidth = pic_width;
                toheight = pic_height;
            }
            else
            ...{
                if(pic_width>pic_height)
                ...{
                    double temp = (double)pic_width/(double)limit_width;
                    towidth = limit_width;
                    toheight = (int)(pic_height/temp);
                }
                else
                ...{
                    double temp = (double)pic_height/(double)limit_height;
                    towidth = (int)(pic_width/temp);
                    toheight = limit_height;
                }
            }
            try
            ...{
                System.Drawing.Bitmap bmp;
                if(thetype == "full")
                ...{
                    bmp = new System.Drawing.Bitmap(limit_width,limit_height);
                }
                else
                ...{
                    bmp = new System.Drawing.Bitmap(towidth,toheight);
                }
                Graphics g = System.Drawing.Graphics.FromImage(bmp);
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
                g.Clear(Color.White);
                if(thetype == "full")
                ...{
                    int temp = towidth - toheight;
                    if(temp>0)
                    ...{
                        g.DrawImage(originalImage,new Rectangle(0,temp/2,towidth,toheight),0,0,pic_width,pic_height,GraphicsUnit.Pixel);
                    }
                    else
                    ...{
                        g.DrawImage(originalImage,new Rectangle(-temp/2,0,towidth,toheight),0,0,pic_width,pic_height,GraphicsUnit.Pixel);
                    }
                }
                else
                ...{
                    g.DrawImage(originalImage,new Rectangle(0,0,towidth,toheight),0,0,pic_width,pic_height,GraphicsUnit.Pixel);
                }
                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                bmp.Save(ms,System.Drawing.Imaging.ImageFormat.Jpeg);
                Response.ClearContent();
                Response.ContentType = "image/Jpeg";
                Response.BinaryWrite(ms.ToArray());
                originalImage.Dispose();
                bmp.Dispose();
                g.Dispose();
            }
            catch
            ...{
                
            }
        }