webservice跨域上传图片

1.上传文件，在一般处理程序中处理

//1.接收post过来的文件
HttpPostedFile file = context.Request.Files[0];
if (file.ContentLength > 0 || file.ContentLength > 1024)
{
    if (file.ContentType.Contains("image/"))
    {
        //2.讲文件转换为文件流
        Stream stream = file.InputStream;
        //3.创建容纳文件流的byte数组
        byte[] buff = new byte[stream.Length];
        //4.将流存储进byte数组中
        stream.Read(buff, 0, buff.Length);
        //5.将byte数组转换为base64字符串
        string strParam = Convert.ToBase64String(buff);
        //6.调用webService方法，传入文件字符串
        srImg.wsImgSoapClient cl = new srImg.wsImgSoapClient();
        int result = cl.AddFile(strParam);
        if (result == 0)
        {
            context.Response.Write("上传成功");
        }
    }
    else
    {
        context.Response.Write("您上传的不是图片类型");
    }
}
else
{
    context.Response.Write("您上传的文件大小错误");
}

2.在webService方法中做如下处理：

#region 通过流保存图片文件
/// <summary>
/// 通过流保存图片文件
/// </summary>
/// <param name="streamStr">文件流字符串</param>
/// <returns></returns>
[WebMethod]
public int AddFile(string streamStr)
{
    //1.将文件字符流转换为byte数组
    byte[] imageBytes = Convert.FromBase64String(streamStr);
    //2.根据数组获取存储区内存流
    MemoryStream stream = new MemoryStream(imageBytes);
    //3.根据file获取stream流，然后根据流生成image对象
    using (Image img = Image.FromStream(stream))
    {
        //设置压缩率
        double rate = 1;
        //开始压缩文件
        return ThumImg(img, rate);
    }
} 

3.通用简单压缩方法，需要搜索更好的优化方法

#region 压缩文件
/// <summary>
/// 压缩文件
/// </summary>
/// <param name="img">图片对象</param>
/// <param name="rate">压缩率</param>
/// <returns></returns>
public int ThumImg(Image img, double rate)
{
    //1.创建新的压缩位图
    using (Image thumImg = new Bitmap((int)(img.Width * rate), (int)(img.Height * rate)))
    {
        using (Graphics g = Graphics.FromImage(thumImg))
        {
            //2.在压缩图片按原图画出缩小版的图
            g.DrawImage(img, new Rectangle(0, 0, thumImg.Width, thumImg.Height), new Rectangle(0, 0, img.Width, img.Height), GraphicsUnit.Pixel);
        }
        //3.存储图片文件
        string phyPath = System.Web.HttpContext.Current.Server.MapPath("/upload/");
        thumImg.Save(phyPath + Guid.NewGuid().ToString() + "." + GetImageFormat(thumImg), System.Drawing.Imaging.ImageFormat.Jpeg);
        return 0;
    }
} 
#endregion

4.通过image对象判断图片后缀方法

#region 返回图片格式（和文件名后缀无关）
/// <summary>
/// 返回图片格式（和文件名后缀无关）
/// </summary>
/// <param name="strImgPath">图片路径及名称</param>
/// <returns>jpeg\gif\bmp\png\tif\icon\wmf</returns>
string GetImageFormat(Image imgSrc)
{
    string strImgFormat = "jpg";
    if (imgSrc.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Jpeg))
        strImgFormat = "jpeg";
    else if (imgSrc.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Gif))
        strImgFormat = "gif";
    else if (imgSrc.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Bmp))
        strImgFormat = "bmp";
    else if (imgSrc.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Png))
        strImgFormat = "png";
    else if (imgSrc.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Tiff))
        strImgFormat = "tiff";
    else if (imgSrc.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Icon))
        strImgFormat = "icon";
    else if (imgSrc.RawFormat.Equals(System.Drawing.Imaging.ImageFormat.Wmf))
        strImgFormat = "wmf";
    return strImgFormat;
} 
#endregion