ASP.NET C# 按原图片大小等比例缩放生成缩略图代码,Asp.Net代码库,德仔网

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【Asp.Net】 ASP.NET C# 按原图片大小等比例缩放生成缩略图
作者:Dezai.CN / 发布于2011/8/22/ 1078
<div>cs页,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.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; 
public partial class test_test_img : System.Web.UI.Page 
{ 
protected void Page_Load(object sender, EventArgs e) 
{ 
//原图片路径 
string source = Server.MapPath("~/images/Source/test1.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, 180,130); 
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(); 
} 
} 
} 
</div>
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　等比例缩放生成缩略图　
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