C#生成缩略图

自已写的简易版本:

<%@ WebHandler Language="C#" Class="ImageUpload" %>

using System;
using System.Web;

public class ImageUpload : IHttpHandler {

public void ProcessRequest (HttpContext context) {
context.Response.ContentType = "text/plain";
//context.Response.Write("Hello World");
HttpPostedFile file = context.Request.Files["imgFile"];

string extName = System.IO.Path.GetExtension(file.FileName);
if(extName!=".jpeg" && extName!=".gif" && extName!=".jpg" && extName!=".png" )
{
context.Response.Write("文件格式不合法!");
return;
}

//生成一张缩略图
System.Drawing.Image image = System.Drawing.Image.FromStream(file.InputStream);

System.Drawing.Bitmap smallImg = new System.Drawing.Bitmap(120, 120);

System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(smallImg);
graphics.DrawImage(image, new System.Drawing.Rectangle(0, 0, 100, 100), new System.Drawing.Rectangle(0, 0, image.Width, image.Height), System.Drawing.GraphicsUnit.Pixel);
string path = "/Upload/Small-" + Guid.NewGuid().ToString() + file.FileName;
smallImg.Save(context.Request.MapPath(path));
System.IO.MemoryStream memoryStream = new System.IO.MemoryStream();
smallImg.Save(memoryStream, System.Drawing.Imaging.ImageFormat.Jpeg);

string uploadImgName = "/Upload/" + Guid.NewGuid().ToString() + file.FileName;
file.SaveAs(context.Request.MapPath(uploadImgName));
context.Response.BinaryWrite(memoryStream.GetBuffer());
context.Response.Write("上传成功!");

}

public bool IsReusable {
get {
return false;
}
}

}

 

工具版本:

using System.Drawing;

namespace WebDemo.Common
{
public class ImageHelper
{

public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
{
System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);

int towidth = width;
int toheight = height;

int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;

switch (mode)
{
case "HW"://指定高宽缩放（可能变形）
break;
case "W"://指定宽，高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case "H"://指定高，宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case "Cut"://指定高宽裁减（不变形）
if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
{
oh = originalImage.Height;
ow = originalImage.Height * towidth / toheight;
y = 0;
x = (originalImage.Width - ow) / 2;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = 0;
y = (originalImage.Height - oh) / 2;
}
break;
default:
break;
}

//新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

//新建一个画板
Graphics g = System.Drawing.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(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(originalImage, new Rectangle(0, 0, towidth, toheight),
new Rectangle(x, y, ow, oh),
GraphicsUnit.Pixel);

try
{
//以jpg格式保存缩略图
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}
}
}

来源：https://www.cnblogs.com/jiangyunfeng/p/10717583.html