Details the sample code for the second edition of the Data URL Generation Tool C # version

Why is there a second edition

First of all, thank Jenlynn students of the message "DATA URL two generation method, C # and HTML5 the same generated base64 code looks different, how can we get them to agree?"

Second, bugs and anomalies were found in the study of the problem.
Bug: Image encoding judgment problem, no matter what extension is the default use of PNG encoding.
Exception: ContextSwitchDeadlock detected

Interface Preview

An improved method for related problems

Image coding and judging problem

Before the main is to forget to get the extension is preceded by a dot.
Related code:

string ext = Path.GetExtension (path) .ToLower ();
                // Determine the encoding format used according to the file extension
                // Note that the extension is dotted!
                switch (ext)
                {
                    case ".gif":
                        fmt = System.Drawing.Imaging.ImageFormat.Gif;
                        break;
                    case ".jpg":
                    case ".jpeg":
                        fmt = System.Drawing.Imaging.ImageFormat.Jpeg;
                        break;
                    case ".ico":
                        fmt = System.Drawing.Imaging.ImageFormat.Icon;
                        break;
                    default:
                        ext = "png";
                        break;
                }
ContextSwitchDeadlock detected
Solution description
StackOverflow mentioned the use of BackgroundWorker, I use threads here; but after testing found: due to performance problems when TextBox displays large text, when the thread interacts with TextBox, if the user does not operate, the window will not die; once there is any operation, the window is Not responding!
So you can only change the solution, use a compromise method, do not let the TextBox display all DataUrl strings, only display a part of them; use a variable "" to save the complete DataUrl string, and copy it to when you click the copy button Windows clipboard.
Related code

        /// <summary>
        /// Used to save the complete DataUrl
        /// </ summary>
        private string fullDataUrl = string.Empty;
Use threads

                // Create thread to generate DataUrl
                System.Threading.Thread thd = new System.Threading.Thread (new ParameterizedThreadStart (buildDataUrl));
                thd.Start (textBox_saveDir.Text);
Use delegation

        /// <summary>
        /// The TextBox delegate is used to achieve thread safety for accessing forms, components, etc. in a thread
        /// </ summary>
        /// <param name = "msg"> </ param>
        public delegate void textbox_delegate (string msg); /// <summary>
        /// The TextBox delegate implementation is used to achieve thread safety for accessing forms and components in threads
        /// </ summary>
        /// <param name = "msg"> </ param>
        public void textboxset (string msg)
        {if (textBox1 == null) return;
        if (textBox1.InvokeRequired)
            {
                textbox_delegate dt = new textbox_delegate (textboxset);
                textBox1.Invoke (dt, new object [] {msg});
            }
            else
            {
            int strLen = msg.Length;
            int step = 100;
            while (strLen> step)
                {
                    textBox1.AppendText (msg.Substring (msg.Length-strLen, step));
                    strLen-= step;
                }
                textBox1.AppendText (msg.Substring (msg.Length-strLen, strLen));
            }
        }
Optimized Base64 encoding

                // Calculate how many characters can be omitted after the Base64 encoded string
                int strLen = str.Length;
                string dyzf = str.Substring (strLen-1, 1);
                while ((dyzf == "A" || dyzf == "=") && strLen> 0)
                {
                    strLen-= 1;
                    dyzf = str.Substring (strLen-1, 1);
                } // Combine the complete Data Url
                fullDataUrl = "<img src = \" data: image / "+ ext +"; base64, "
                    + str.Substring (0, strLen)
                    + "\" width = \ "" + img.Width + "\" height = \ "" + img.Height + "\" /> ";
                    // The TextBox is defined to display only 20,000 characters at most, and the extra cut will not be displayed, otherwise the performance is too poor.
                int showLen = 20000; if (showLen> fullDataUrl.Length)
                {
                    showLen = fullDataUrl.Length;
                }
                textboxset (fullDataUrl.Substring (0, showLen));
        /// <summary>
        /// Copy the complete Data Url to the Windows clipboard.
        /// </ summary>
        /// <param name = "sender"> </ param>
        /// <param name = "e"> </ param>
        private void button_copy_Click (object sender, EventArgs e)
        {
            Clipboard.SetText (fullDataUrl);
        }
        /// <summary>
        /// Clear the text box
        /// </ summary>
        /// <param name = "sender"> </ param>
        /// <param name = "e"> </ param>
        private void button_clear_Click (object sender, EventArgs e)
        {
            textBox1.Clear ();
            fullDataUrl = string.Empty;
        }