Dot Net Thoughts

While playing around one of hobby project, I found there is a nice color picker dropdown available in WordPad, for setting the font color. I was using Windows

Color Dialog. So I thought of implementing a WordPad like color picker. And I think I almost readed my goal. I need to try this in the Toolstrip dropdown too.

//On the Form load I am loading the colors to the Dropdown.
//You can also bind the p to the Dropdown.
Type t = typeof(Color);
PropertyInfo[] p = t.GetProperties();
foreach (PropertyInfo item in p)
{
    if (item.PropertyType.FullName.Equals("System.Drawing.Color", StringComparison.CurrentCultureIgnoreCase))
    {
        this.comboBox1.Items.Add(item.Name);
    }
}

And I set the Dropdown’s DrawMode property to “OwnerDrawFixed”. And in the DrawItem event of the Dropdown I wrote the code.

if (e.Index != -1)
{
    e.DrawBackground();
    e.Graphics.FillRectangle(GetCurrentBrush(comboBox1.Items[e.Index].ToString()), e.Bounds);
    Font f = comboBox1.Font;
    e.Graphics.DrawString(comboBox1.Items[e.Index].ToString(), f, Brushes.Black, e.Bounds, StringFormat.GenericDefault);
    e.DrawFocusRectangle();
}

And the GetCurrentBrush() function returns the Brush for painting the rectangle. You can write the code in the DrawItem event too, but initialy I thought about setting the font color using the same color. But later that idea changed.

private Brush GetCurrentBrush(string colorName)
{
    return new SolidBrush(Color.FromName(colorName));
}

One issue I found in this code is, for black color, I can’t see the color name. And here is the screenshot of Color Picker Dropdown running on my machine.

Color Picker Dropdown screenshot

Sometimes we will get nice Images from Web as Icons. But we can’t use these Images as application icons in .Net, because the .Net supports *.ico(Icon) format only. This code will convert an Image to Icon using C#. It is written .Net Framework 3.5, but it should work in .Net 2.0. It supports Images upto size 128×128. And supports various image formats(*.jpg,*.gif, *.png. *.bmp).

using System;
using System.Drawing;
using System.IO;

string fileName, newFileName;
fileName = "C:\Sample.jpg";
newFileName = Path.ChangeExtension(fileName, ".ico");
using (Bitmap bitmap = Image.FromFile(fileName, true) as Bitmap)
{
    using (Icon icon = Icon.FromHandle(bitmap.GetHicon()))
    {
        using (Stream imageFile = File.Create(newFileName))
        {
            icon.Save(imageFile);
            Console.WriteLine("Converted - {0}", newFileName);
        }
    }
}

Code it pretty self explanatory. Let me know if you have faced any issues.

Few days back, I got some question related to Captcha (security mechanism, which helps web masters to avoid spam) in a Forum. So I thought of implementing one. I got few nice scripts in Code Project, its a simple implementation, no too much logic and not too complex to understand. Also I am using an HTTP Handler instead of ASPX Page, for the implementation.

using (Bitmap b = new Bitmap(150, 40, PixelFormat.Format32bppArgb))
        {
            using (Graphics g = Graphics.FromImage(b))
            {
                Rectangle rect = new Rectangle(0, 0, 149, 39);
                g.FillRectangle(Brushes.White, rect);

                // Create string to draw.
                Random r = new Random();
                int startIndex = r.Next(1, 5);
                int length = r.Next(5, 10);
                String drawString = Guid.NewGuid().ToString().Replace("-", "0").Substring(startIndex, length);

                // Create font and brush.
                Font drawFont = new Font("Arial", 16, FontStyle.Italic | FontStyle.Strikeout);
                using (SolidBrush drawBrush = new SolidBrush(Color.Black))
                {
                    // Create point for upper-left corner of drawing.
                    PointF drawPoint = new PointF(15, 10);

                    // Draw string to screen.
                    g.DrawRectangle(new Pen(Color.Red, 0), rect);
                    g.DrawString(drawString, drawFont, drawBrush, drawPoint);
                }
                b.Save(context.Response.OutputStream, ImageFormat.Jpeg);
                context.Response.ContentType = "image/jpeg";
                context.Response.End();
            }
        }

I wrote the code in the Process Request event in HTTPHandler.
And to use this in your pages you can create an IMG tag with src attribute pointing to this.

<img src="myhandler.ashx" />

Note: Some time ASP.Net caches the image, so you may need to pass some GUID as querystring in the Handler.

Update: Sometime we may need to refresh the Captcha image, without post back, here is a simple javascript which will refresh the captcha image without post back.

<script type="text/javascript">
        function RefreshCaptcha() {
            var img = document.getElementById("imgCaptcha");
            img.src = "Handler.ashx?query=" + Math.random();
        }
</script>
<div>
<img src="Handler.ashx" id="imgCaptcha" />
<a href="#" onclick="javascript:RefreshCaptcha();">Refresh</a>
</div>

Here is the screenshot of web page using Captcha.

Captcha - Security Image using ASP.Net and C#

Recently I got a chance to work on Windows Application, it is Twitter client using C#. In that I need to show some Image from a URL. I thought like Microsoft will provide some way to load Images from URL and I tried to do the same with “Image.FromFile” method. But it failed. Then I searched and found it will not supports Urls. So I developed an extention method for Image class, which will load from URL. I tried to Inherit from Image class, but that doesn’t work, it is not inheritable.

And here is the code

namespace dotnetthoughts
{
	public static class Utilities
	{
		public static Image FromURL(this Image image, string Url)
		{
			HttpWebRequest request = HttpWebRequest.Create(Url) as HttpWebRequest;
			HttpWebResponse respone = request.GetResponse() as HttpWebResponse;
			return Image.FromStream(respone.GetResponseStream(),true);
		}
		public static Image FromURL(this Image image, string Url, string userName, string Password)
		{
			HttpWebRequest request = HttpWebRequest.Create(Url) as HttpWebRequest;
			request.Credentials = new NetworkCredential(userName, Password);
			HttpWebResponse respone = request.GetResponse() as HttpWebResponse;
			return Image.FromStream(respone.GetResponseStream(), true);
		}
	}
}

In the second method, I am accepting the Username and Password, so it can access protected Images too.

Implementation of this code

//If we don't put null, C Sharp compiler will not allows to compile the application
Image img = null;
this.pictureBox1.Image = img.FromURL(this.textBox1.Text);

Few days back, I got a requirement to implement Free Hand drawing in .Net. I searched a lot but I didn’t get any good solution, the one I found from code project was Invalidating the picture box every time. So today I got a solution, it not seems to be a perfect solution because Paint events occurs, we need to re-paint the whole lines again.

I am attaching the code here. I will update the post once I get some perfect solution for this.

 Private m_Drawing As Boolean = False
    Private m_List As List(Of Point) = Nothing
    Private Sub MyPic_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyPic.MouseDown
        If e.Button = Windows.Forms.MouseButtons.Left Then
            m_Drawing = True
        End If
    End Sub
    Private Sub MyPic_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyPic.MouseUp
        If m_Drawing AndAlso m_List IsNot Nothing Then
            If m_List.Count >= 2 Then
                MyPic.CreateGraphics.DrawLines(New Pen(Color.Blue, 1), m_List.ToArray())
            End If
            m_Drawing = False
            m_List.Clear()
        End If
    End Sub

    Private Sub MyPic_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyPic.MouseMove
        If m_List IsNot Nothing AndAlso m_Drawing Then
            m_List.Add(e.Location)
        End If
    End Sub
    Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        m_List = New List(Of Point)
    End Sub

Code is pretty self explanatory. So I am not putting any comments

Remember old BitBlt API, for capturing screens? Here is the solution from Microsoft on .Net framework 2.0. CopyFromScreen Method – Performs a bit-block transfer of color data from the screen to the drawing surface of the Graphics.

Rectangle region = new Rectangle(0, 0, SystemInformation.VirtualScreen.Width, SystemInformation.VirtualScreen.Height);
using (Bitmap bitmap = new Bitmap(region.Width, region.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb))
using (Graphics bitmapGraphics = Graphics.FromImage(bitmap))
{
bitmapGraphics.CopyFromScreen(region.Left, region.Top, 0, 0, region.Size);
Clipboard.SetImage(bitmap);
}

It only works with .Net 2.0 and more.

I developed an Application, which hosted in Codeplex, called captureit., which is using this code for capturing desktop.

MSDN : http://msdn2.microsoft.com/en-us/library/system.drawing.graphics.copyfromscreen.aspx