缩略图实现方案

using System;
using System.Configuration;
using System.Collections.Generic;
using System.Text;
using System.Net.Mail;
using System.IO;
using System.Drawing;

namespace Utility
{
    public class ImageHelper
    {
        public static Image GnerateImage(Stream stream, int width, int height)
        {
            Image image = Image.FromStream(stream);
            int x, y;
            int nowWidth = 0;
            int nowHeight = 0;
            if (image.Height <= height && image.Width <= width)
            {
                return image;
            }
            else
            {
                if (image.Width / (double)image.Height > width / (double)height)
                {
                    nowHeight = image.Height;
                    nowWidth = image.Height * width / height;
                    y = 0;
                    x = (image.Width - nowWidth) / 2;
                }
                else
                {
                    nowWidth = image.Width;
                    nowHeight = image.Width * height / width;
                    x = 0;
                    y = (image.Height - height) / 2;
                }

                //新建一个bmp图片
                Image bitmap = new Bitmap(width, height);

                //新建一个画板
                Graphics g = Graphics.FromImage(bitmap);

                //设置高质量插值法
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

                //设置高质量,低速度呈现平滑程度
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                //清空画布并以透明背景色填充
                g.Clear(System.Drawing.Color.Transparent);

                //在指定位置并且按指定大小绘制原图片的指定部分
                g.DrawImage(image, new Rectangle(0, 0, width, height),
                    new Rectangle(x, y, nowWidth, nowHeight),
                   GraphicsUnit.Pixel);
                g.Dispose();
                return bitmap;
            }
        }
    }
}

缩略图实现方案