"
http://www.w3.org/1999/xhtml
"
>
<meta http-equiv=
"
Content-Type
"
content=
"
text/html; charset=utf-8
"
/>
<title></title>
</head>
<form action=
"
Getmin.ashx
"
method=
"
post
"
enctype=
"
multipart/form-data
"
>
图片:
<input type=
"
file
"
name=
"
file
"
id=
"
file
"
onchange=
"
javascript:fileInfo();
"
/>
<p style=
"
font-size:12px;
"
>原图宽:<label id=
"
ow
"
>
0
</label> 原图高:<label id=
"
oh
"
>
0
</label>&
nbsp;
原图大小:
<label id=
"
os
"
>
0
</label>KB</p>
<p>设置宽度:<input type=
"
text
"
name=
"
width
"
style=
"
width:50px;
"
/>
<span style=
"
color:#09a02c;font-size:12px
"
>高度按原图比例折算</span></p>
<p><input type=
"
submit
"
style=
"
color:#ff6a00
"
value=
"
下载缩略图
"
/> </p>
</form>
</body>
</html>
<script type=
"
text/javascript
"
>
//
上传前获取图片信息(用html5的File)
function fileInfo() {
var
f = document.getElementById(
"
file
"
).files[
0
];
var
reader =
new
FileReader();
reader.readAsDataURL(f);
reader.onload
=
function (e) {
var
data =
e.target.result;
//
加载一个图片获取宽度高度
var
image =
new
Image();
image.src
=
data;
image.onload
=
function () {
var
width =
image.width;
var
height =
image.height;
var
size = parseInt(f.size /
1024
);
document.getElementById(
"
ow
"
).innerHTML =
width;
document.getElementById(
"
oh
"
).innerHTML =
height;
document.getElementById(
"
os
"
).innerHTML =
size;
</script>
2.添加一个一般处理程序:Getmin.ashx
public void ProcessRequest(HttpContext context)
//1.获取用户上传的文件流
HttpPostedFile file = context.Request.Files[0];
//获取文件名
string fileName = file.FileName;
//获取扩展名
string Extension = Path.GetExtension(fileName).ToUpper();
//2.根据用户上传的文件流创建一个图片
using (Image originalImage = Image.FromStream(file.InputStream))
//获取原始图片的宽和高
int owidth = originalImage.Width;
int oheight = originalImage.Height;
//缩略图的宽
int mwidth = Convert.ToInt32(context.Request.Form["width"]);
//等比例的高,取整数
int mheight = mwidth * oheight / owidth;
//3.根据原始图片，等比例创建一个缩小后的图片
using (Image minImage = new Bitmap(mwidth, mheight))
//4.把大图片内容画到小图片上
//基于小图创建一个画布对象
Graphics gmin = Graphics.FromImage(minImage);
//把大图画到小图上
gmin.DrawImage(originalImage, 0, 0, mwidth, mheight);
//5.下载缩略图
MemoryStream ms = new MemoryStream();
//判断图片类型
ImageFormat imageFormat = null;
string ContentType = "";
switch (Extension)
case ".JPG": imageFormat = ImageFormat.Jpeg; ContentType = "image/jpeg"; break;
case ".PNG": imageFormat = ImageFormat.Png; ContentType = "image/png"; break;
case ".GIF": imageFormat = ImageFormat.Gif; ContentType = "image/gif"; break;
//................如需要其他图片格式继续添加
minImage.Save(ms,imageFormat);
context.Response.ClearContent();
context.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
context.Response.ContentType=ContentType;
context.Response.BinaryWrite(ms.ToArray());
context.Response.End();
public bool IsReusable
return false;
代码注释已经很清晰了，所以也不一一解析了。
3.1挑一张计算机里的图片:
3.2上传前:
3.3把宽度设成200后点击下载
3.4查看已经下载的文件
demo下载:http://pan.baidu.com/s/1jHiIXuQ 提取密码:fewx
