读取数据库图片显示、缩小、更新代码,C#代码库,德仔网

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【C#】读取数据库图片显示、缩小、更新
作者:ailsa / 发布于2016/8/4/ 601
ashx源文件代码：

<%@ WebHandler Language="C#" Class="GetThumbnailImageByEmpCode" %>  
  
using System;  
using System.Web;  
using System.Data.SqlClient;  
using System.Data;  
using System.Drawing;  
using System.Drawing.Drawing2D;  
using System.IO;  
using System.Drawing.Imaging;  
  
public class GetThumbnailImageByEmpCode : IHttpHandler  
{  
  
    public void ProcessRequest(HttpContext context)  
    {  
        if (context.Request.QueryString["code"] == null)  
        {  
            return;  
        }  
        int newWidth = 336;         //目标图片宽度  
        int newHeight = 252;        //目标图片高度  
        bool bNeedUpdate = false;   //是否需要更新数据库  
        System.Drawing.Image Img;  
        using (SqlConnection conn = new SqlConnection(db.ConnectionStrings.hrConnectionString))  
        using (SqlCommand cmd = new SqlCommand("", conn))  
        {  
            cmd.CommandText = "select photo from ZlEmployee where code=@code and DATALENGTH(photo)>1000";  
            cmd.Parameters.AddWithValue("code", context.Request.QueryString["code"]);  
            conn.Open();  
            SqlDataReader reader = cmd.ExecuteReader();  
            if (reader.Read())  
            {  
                byte[] imgData = (byte[])reader[0];  
                reader.Close();  
  
                using (MemoryStream ms = new MemoryStream(imgData))  
                {  
                    Img = System.Drawing.Image.FromStream(ms);  
                }  
                  
                if (Img.Width > newWidth || Img.Height > newHeight)  
                {  
                    Img = reSizeImage(Img);  
                    bNeedUpdate = true;  
                }  
  
                using (MemoryStream ms = new MemoryStream())  
                {  
                    #region 输出图片到浏览器  
                    Bitmap jpg = new Bitmap(Img);  
                    jpg.Save(ms, ImageFormat.Jpeg);  
                    context.Response.Clear();  
                    context.Response.Charset = "utf-8";  
                    context.Response.ContentType = "image/pjpeg";  
                    context.Response.BinaryWrite(ms.ToArray());  
                    #endregion  
                    //检查是否需要更新  
                    if (bNeedUpdate)  
                    {  
                        cmd.CommandText = "update ZlEmployee set photo=@photo where code=@code";  
                        cmd.Parameters.Clear();  
                        cmd.Parameters.AddWithValue("code", context.Request.QueryString["code"]);  
                        cmd.Parameters.AddWithValue("photo", ms.ToArray());  
                        cmd.ExecuteNonQuery();  
                    }  
                }  
                context.Response.End();  
            }  
        }  
    }  
  
    public System.Drawing.Image reSizeImage(System.Drawing.Image img)  
    {  
        int newWidth = 336;  
        int newHeight = 252;  
  
        //如果是高度大于宽度则按竖图处理，宽小于高  
        if (img.Height > img.Width)  
        {  
            newWidth = 252;  
            newHeight = 336;  
        }  
 
        #region 计算按比例缩放的图片尺寸  
        if (img.Height / img.Width > newHeight / newWidth)  
        {  
            newWidth = newHeight * img.Width / img.Height;  
        }  
        else  
        {  
            newHeight = img.Height * newWidth / img.Width;  
        }  
        #endregion  
 
        #region 缩放图片  
        using (System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap((int)newWidth, (int)newHeight, PixelFormat.Format32bppArgb)) //using   3   
        {  
            using (System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(bitmap))  
            {  
                //清除整个绘图面并以透明背景色填充   
                graphics.Clear(Color.Transparent);  
                //在指定位置并且按指定大小绘制   原图片   对象   
                graphics.DrawImage(img, new Rectangle(0, 0, (int)newWidth, (int)newHeight));  
                using (MemoryStream ms = new MemoryStream())  
                {  
                    bitmap.Save(ms, ImageFormat.Jpeg);  
                    return System.Drawing.Image.FromStream(ms);  
                }  
            }  
        }  
        #endregion  
    }  
    public bool IsReusable  
    {  
        get  
        {  
            return false;  
        }  
    }  
}
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