iphone向Web服务器发送图片

//把图片转换为NSData  
UIImage *image = [UIImage imageNamed:@"vim_go.png"];      
NSData *imageData = UIImagePNGRepresentation(image);  
// post url  
NSString *urlString = @"http://10.28.4.162/test-upload.php";  
  
// setting up the request object now  
NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease];  
[request setURL:[NSURL URLWithString:urlString]];  
[request setHTTPMethod:@"POST"];  
//  
NSString *boundary = [NSString stringWithString:@"---------------------------14737809831466499882746641449"];  
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];  
[request addValue:contentType forHTTPHeaderField: @"Content-Type"];  
//  
NSMutableData *body = [NSMutableData data];  
[body appendData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];      
[body appendData:[[NSString stringWithString:@"Content-Disposition: form-data; name="userfile"; filename="vim_go.png"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];  
[body appendData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];  
[body appendData:[NSData dataWithData:imageData]];  
[body appendData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];  
[request setHTTPBody:body];  
  
NSLog(@"%@",body);  
NSLog(@"%@",request); 

NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];  

NSString *returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];  
  
result_btn.text = returnString;