ms.GetBuffer() 是把内存里边的东西，保存为2进制格式吗？
ms.GetBuffer() 是把内存里边的东西，保存为2进制格式吗？
ms = new MemoryStream();
final_image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
Thumbnail thumb = new Thumbnail(thumbnail_id, ms.GetBuffer() );
using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;
using System.Collections.Generic;
public partial class upload : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
System.Drawing.Image thumbnail_image = null;
System.Drawing.Image original_image = null;
System.Drawing.Bitmap final_image = null;
System.Drawing.Graphics graphic = null;
MemoryStream ms = null;
try
{
// Get the data 得到上传的文件
HttpPostedFile jpeg_image_upload = Request.Files["Filedata"];
// Retrieve the uploaded image 把上传文件转化为 Image
original_image = System.Drawing.Image.FromStream(jpeg_image_upload.InputStream);
// Calculate the new width and height 下边一整段，都是计算长宽的,具体算法没有深究
int width = original_image.Width; //原始宽度
int height = original_image.Height; //原始长度
int target_width = 200;
int target_height = 200;
int new_width, new_height;
float target_ratio = (float)target_width / (float)target_height; //目标 宽长比
float image_ratio = (float)width / (float)height; //原始 宽长比
if (target_ratio > image_ratio) //计算出新的长宽。
{
new_height = target_height;
new_width = (int)Math.Floor(image_ratio * (float)target_height);
}
else
{
new_height = (int)Math.Floor((float)target_width / image_ratio);
new_width = target_width;
}
new_width = new_width > target_width ? target_width : new_width;
new_height = new_height > target_height ? target_height : new_height;
// Create the thumbnail 创建缩略图
// Old way
//thumbnail_image = original_image.GetThumbnailImage(new_width, new_height, null, System.IntPtr.Zero);
// We don't have to create a Thumbnail since the DrawImage method will resize, but the GetThumbnailImage looks better
// I've read about a problem with GetThumbnailImage. If a jpeg has an embedded thumbnail it will use and resize it which
// can result in a tiny 40x40 thumbnail being stretch up to our target size
final_image = new System.Drawing.Bitmap(target_width, target_height); //创建指定大小的位图
graphic = System.Drawing.Graphics.FromImage(final_image); //为什么要通过Bitmap转一下? 应该是可以动态画画
//黑色的画笔,在graphic内画一个指定的矩形
graphic.FillRectangle(new System.Drawing.SolidBrush(System.Drawing.Color.Black), new System.Drawing.Rectangle(0, 0, target_width, target_height));
int paste_x = (target_width - new_width) / 2;
int paste_y = (target_height - new_height) / 2;
graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; /* new way */ //一个图像插值算法
//graphic.DrawImage(thumbnail_image, paste_x, paste_y, new_width, new_height);
graphic.DrawImage(original_image, paste_x, paste_y, new_width, new_height); //载入原始图，按指定大小重新绘制
// Store the thumbnail in the session (Note: this is bad, it will take a lot of memory, but this is just a demo)
ms = new MemoryStream();
final_image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);//不明白，这里并没有建立什么联系？？？
// Store the data in my custom Thumbnail object
string thumbnail_id = DateTime.Now.ToString("yyyyMMddHHmmssfff"); //设置文件名
Thumbnail thumb = new Thumbnail(thumbnail_id, ms.GetBuffer());
// Put it all in the Session (initialize the session if necessary)
List<Thumbnail> thumbnails = Session["file_info"] as List<Thumbnail>;
if (thumbnails == null)
{
thumbnails = new List<Thumbnail>();
Session["file_info"] = thumbnails;
}
thumbnails.Add(thumb);
Response.StatusCode = 200;
Response.Write(thumbnail_id);
}
catch
{
// If any kind of error occurs return a 500 Internal Server error
Response.StatusCode = 500;
Response.Write("An error occured");
Response.End();
}
finally
{
// Clean up
if (final_image != null) final_image.Dispose();
if (graphic != null) graphic.Dispose();
if (original_image != null) original_image.Dispose();
if (thumbnail_image!= null )thumbnail_image.Dispose();
if (ms != null) ms.Close();
Response.End();
}
}
}
