利用HttpWebRequest/HttpWebResponse获得指定url资源的一个问题
Posted on 2006-02-20 13:38 alittlefish 阅读(3973) 评论(7) 编辑 收藏 举报前阵子帮朋友找图片,写了个小程序抓图片资源。但是过程中碰到了个小问题。通过HttpWebResponse.GetResponseStream()获得的流保存成文件却显示不出原来的图片。
Uri myUri = new Uri(“http://www.xxx.com/xx.jpg");
HttpWebRequest myWebRequest= (HttpWebRequest)WebRequest.Create(myUri);
myWebRequest.Method = "GET";
HttpWebResponse myWebResponse= (HttpWebResponse)myWebRequest.GetResponse();
StreamReader reader = new StreamReader(myWebResponse.GetResponseStream(),Encoding.ASCII);
byte[] buffer = Encoding.ASCII.GetBytes(reader.ReadToEnd());
FileInfo file = new FileInfo(@"C:\xxx.jpg");
BinaryWriter writer = new BinaryWriter(file.Open(FileMode.Create, FileAccess.Write));
writer.Write(buffer, 0, buffer.Length);
writer.Close();
HttpWebRequest myWebRequest= (HttpWebRequest)WebRequest.Create(myUri);
myWebRequest.Method = "GET";
HttpWebResponse myWebResponse= (HttpWebResponse)myWebRequest.GetResponse();
StreamReader reader = new StreamReader(myWebResponse.GetResponseStream(),Encoding.ASCII);
byte[] buffer = Encoding.ASCII.GetBytes(reader.ReadToEnd());
FileInfo file = new FileInfo(@"C:\xxx.jpg");
BinaryWriter writer = new BinaryWriter(file.Open(FileMode.Create, FileAccess.Write));
writer.Write(buffer, 0, buffer.Length);
writer.Close();
开始用Encoding.Default,取出来的字节流长度(buffer.Length)和原始图片的长度(myWebRequest.ContentLength)都不符,很明显是Encoder的问题,换了ASCII,长度一致了,但是还是无法显示。把Reader对象Reflect了一下,又看了以下Encoding.ASCII,发现其GetBytes里有这么一段:
while (charIndex < num1)
{
char ch1 = chars[charIndex++];
if (ch1 >= '\x0080')
{
ch1 = '?';
}
bytes[byteIndex++] = (byte) ch1;
}
{
char ch1 = chars[charIndex++];
if (ch1 >= '\x0080')
{
ch1 = '?';
}
bytes[byteIndex++] = (byte) ch1;
}
原来的字节流并不是原封不动的被保存了,结果肯定会无法显示正常的图片。
没办法只好换了个办法,直接用Bitmap对象来保存图片。虽然结果是没问题了。但是之前的这种保存方式难道就完全不可行了吗?不知道哪位高人可以给一个正解。