<%@ Page Language="C#" AutoEventWireup="true" CodeFile="test_img.aspx.cs" Inherits="test_test_img" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>缩略图测试</title>
</head>
<body style="text-align:center;">
<form id="form1" runat="server">
原图:<br />
<asp:Image ID="Image1" runat="server" />
<br />
缩略图:<br />
<asp:Image ID="Image2" runat="server" />
<br />
</form>
</body>
</html>
以下这个缩略图函数生成后空白部分是用背景色填充的.
using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Text;
namespace cha_net.admin
{
public partial class aa : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
//原图片路径
string source = Server.MapPath("~/images/1.jpg");
string type = "";
//获取原图片格式
string fileExtension = System.IO.Path.GetExtension(source).ToLower();
switch (fileExtension)
{
case ".gif": type = ".gif"; break;
case ".jpg": type = ".jpg"; break;
case ".bmp": type = ".bmp"; break;
case ".png": type = ".png"; break;
}
//缩略图保存位置和文件名,图片格式
string small = Server.MapPath("~/images/Small/Small_test" + type);
MakeThumbnail(source, small, 90, 130);
Image1.ImageUrl = source;
Image2.ImageUrl = small;
}
/**/
//// <summary>
/**/
/// 生成缩略图
/**/
/// </summary>
/**/
/// <param name="originalImagePath">源图路径（物理路径）</param>
/**/
/// <param name="thumbnailPath">缩略图路径（物理路径）</param>
/**/
/// <param name="width">缩略图宽度</param>
/**/
/// <param name="height">缩略图高度</param>
public void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height)
{
//获取原始图片
System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
//缩略图画布宽高
int towidth = width;
int toheight = height;
//原始图片写入画布坐标和宽高(用来设置裁减溢出部分)
int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;
//原始图片画布,设置写入缩略图画布坐标和宽高(用来原始图片整体宽高缩放)
int bg_x = 0;
int bg_y = 0;
int bg_w = towidth;
int bg_h = toheight;
//倍数变量
double multiple = 0;
//获取宽长的或是高长与缩略图的倍数
if (originalImage.Width >= originalImage.Height) multiple = (double)originalImage.Width / (double)width;
else multiple = (double)originalImage.Height / (double)height;
//上传的图片的宽和高小等于缩略图
if (ow <= width && oh <= height)
{
//缩略图按原始宽高
bg_w = originalImage.Width;
bg_h = originalImage.Height;
//空白部分用背景色填充
bg_x = Convert.ToInt32(((double)towidth - (double)ow) / 2);
bg_y = Convert.ToInt32(((double)toheight - (double)oh) / 2);
}
//上传的图片的宽和高大于缩略图
else
{
//宽高按比例缩放
bg_w = Convert.ToInt32((double)originalImage.Width / multiple);
bg_h = Convert.ToInt32((double)originalImage.Height / multiple);
//空白部分用背景色填充
bg_y = Convert.ToInt32(((double)height - (double)bg_h) / 2);
bg_x = Convert.ToInt32(((double)width - (double)bg_w) / 2);
}
//新建一个bmp图片,并设置缩略图大小.
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
//新建一个画板
System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
//设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
//设置高质量,低速度呈现平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
//清空画布并设置背景色
g.Clear(System.Drawing.ColorTranslator.FromHtml("#F2F2F2"));
//在指定位置并且按指定大小绘制原图片的指定部分
//第一个System.Drawing.Rectangle是原图片的画布坐标和宽高,第二个是原图片写在画布上的坐标和宽高,最后一个参数是指定数值单位为像素
g.DrawImage(originalImage, new System.Drawing.Rectangle(bg_x, bg_y, bg_w, bg_h), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel);
try
{
//获取图片类型
string fileExtension = System.IO.Path.GetExtension(originalImagePath).ToLower();
//按原图片类型保存缩略图片,不按原格式图片会出现模糊,锯齿等问题.
switch (fileExtension)
{
case ".gif": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif); break;
case ".jpg": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); break;
case ".bmp": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp); break;
case ".png": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png); break;
}
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}
}
}
