一个.net 压缩位图至JPEG的代码

首先准备一张位图图像source.bmp，将它保存在bmp.aspx同一目录中

<%@ Page language="c#" %>
<%@ Import Namespace="System.Drawing" %>
<%@ Import Namespace="System.Drawing.Imaging" %>

<script language="c#" runat="server">

private void Page_Load(object sender, System.EventArgs e)
{

// 设置 mime 类型为image/jpeg，即将向浏览器输出JPGE格式的图像
Response.Clear();
Response.ContentType="image/jpeg";

Bitmap OutputBitmap = new Bitmap(Server.MapPath("source.bmp"));//新建BitMap对象
System.Drawing.Imaging.EncoderParameters encoderParams = new System.Drawing.Imaging.EncoderParameters();
long[] quality = new long[1];

int comp = 0;
if (Request.QueryString["comp"] != "") { comp = Convert.ToInt16(Request.QueryString["comp"]); }
quality[0] = comp; //0 to 100 最高质量为100
System.Drawing.Imaging.EncoderParameter encoderParam = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);
encoderParams.Param[0] = encoderParam;

ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();//获得包含有关内置图像编码解码器的信息的ImageCodecInfo 对象。
ImageCodecInfo jpegICI = null;
for (int x = 0; x < arrayICI.Length; x++)
{
if (arrayICI[x].FormatDescription.Equals("JPEG"))
{
jpegICI = arrayICI[x];//设置JPEG编码
break;
}
}

if (jpegICI != null)
{
OutputBitmap.Save(Response.OutputStream, jpegICI, encoderParams);//将位图对象以流格式并用JPEG编解码参数保存到输出流。

}

// clean up
OutputBitmap.Dispose();

}
</script>
在浏览器地址输入：http://localhost/bmp.aspx?comp=0
将会看到图像，调整comp的值，将会看到不同的效果.