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  • 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();
    }
    }
    }
    }

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  • 原文地址:https://www.cnblogs.com/jiangyunfeng/p/10717583.html
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