URI 到位图 C# ASP.NET

URI to Bitmap C# ASP.NET

我正在使用 webcam.js 在 ASP.NET MVC 中捕获 URI。我想将此 URI 转换为 C# 中的位图。下面是我当前尝试将 URI 解析为位图的代码,但是它在创建字节缓冲区时给出了错误 "Invalid length for a Base-64 char array or string"。我也试过将它作为 C# Uri 类型引入,但没有成功。

[HttpPost]
public JsonResult Scan(string file)
{
   Bitmap img = null;
   var matchGroups = Regex.Match(file, @"^data:((?<type>[\w\/]+))?;base64,(?<data>.+)$").Groups;
   var base64Data = matchGroups["data"].Value;
   byte[] byteBuffer = Convert.FromBase64String(base64Data);
   MemoryStream memoryStream = new MemoryStream(byteBuffer);
   memoryStream.Flush();
   memoryStream.Position = 0;
   img = (Bitmap)Bitmap.FromStream(memoryStream);
}

这是我从 webcam.js 对象 data_uri 发布的 URI,它在 html.

中很好地呈现图像
data:image/jpeg;base64,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 q2GiAMgrLbb5Oix4hx4UrBAPgKMD4/ZPYcxOE3ow52oDYa3ERwnNJBjgKIERPgLLak4jCl6f6CzZD/0WTByeVrh3sU8PkRGVnLTVBZITtbgJtMyD5lMc/wCnnKa0kHJ/qo yVCJZIOE3dHlMDjJ9j5SJjjlJuQDyNo55WHu3gCVGST5KcPupq3bQWZjaMrLHQclNMH2KyOQAqpILJN/7JoeI9/usE5hNM xRgB7qkgCSE6lBJnnwVCTMf6rIcWOx 3uqUU wPQZUERPCkD4iCta3eHEGIU5dBwFhLTk3yWiVrjBkrEyOcJmfdNg OVjlMokJjEJjojylJCTnOBnwVLd9AKQWxAWA7YJ5WC4 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感谢您的帮助!

您的正则表达式不正确。

base-64 数据在数据 URI 中的 base64, 之后开始。注意逗号。您的正则表达式在 data 捕获组中包含逗号。你需要把它放在捕获组外面:

@"^data:((?<type>[\w\/]+))?;base64,(<data>.+)$"
[HttpPost]
        public JsonResult Scan(string file)
        {
            byte[] data = Convert.FromBase64String(file.Substring(file.LastIndexOf(',') + 1));
            Image image;
            Bitmap bitmap;
            using (MemoryStream ms = new MemoryStream(data))
            {
                image = Image.FromStream(ms);
                bitmap = new Bitmap(image);
            }
        }