.NET LCD MatrixControl and GDI+

• Download source files - 32.2 Kb
• Download demo project - 18 Kb

Introduction

Once, it was required for me, a control similar to LCD, for data presentation. Having looked in the Internet, I found a nice realization from Nic Wilson. But the code was written in C++, and my project was in C#. Therefore, I decided to rewrite Nic's code, and at the same time I wanted to estimate how quick GDI+ works in .NET.

Using the code

In your project, you need to refer to the library with our control, then you should place the control in design time in your project.

After you finish with design time, start initializing our control in the constructor.

public Form1()
{
  InitializeComponent();
  BkColor = Color.FromArgb(R,G,B);
  OnColor = Color.FromArgb(R,G,B);
  OffColor = Color.FromArgb(R,G,B);
  //Set up initial text.
  this.matrixControl1.ScreenText = " Info Text ";
  //In this case pad symbol is empty.
  matrixControl1.SetAutoPadding(true,' ');
  //If you want immeditely start scrolling, 
  //please uncomment next line.
  //matrixControl1.DoScroll(1000, 
  //    MatrixLib.MatrixControl.ScrollDirection.Left);
}

The main "magic" occurs in a method OnPaint.

protected override void OnPaint(PaintEventArgs pea) 
{
  Rectangle m_rect = this.DisplayRectangle;
  //Create buffer image
  Bitmap _buffImage = new Bitmap(m_rect.Width,m_rect.Height);
  Graphics _buff = Graphics.FromImage(_buffImage);
  int x = 0, y = 0;
  int strlen = m_StrText.Length;
  if (strlen == 0)
    return;
  //Create array of color maps
  System.Drawing.Imaging.ColorMap []_ColorMap = 
            new System.Drawing.Imaging.ColorMap[3];
  _ColorMap[0] = new System.Drawing.Imaging.ColorMap();
  _ColorMap[1] = new System.Drawing.Imaging.ColorMap();
  _ColorMap[2] = new System.Drawing.Imaging.ColorMap();
  _ColorMap[0].OldColor = SEGM_COLORS[0];
  _ColorMap[0].NewColor = m_crOnColor;
  _ColorMap[1].OldColor = SEGM_COLORS[1];
  _ColorMap[1].NewColor = m_OffColor;
  _ColorMap[2].OldColor = SEGM_COLORS[2];
  _ColorMap[2].NewColor = m_crBackColor;
  
  //Obtain image attributes
  System.Drawing.Imaging.ImageAttributes bmpAttr = 
          new System.Drawing.Imaging.ImageAttributes();
  try
  {
    bmpAttr.SetRemapTable(_ColorMap);
  }
  catch(System.Exception ex)
  {
    Debug.Fail(ex.Message);
  }
  int charcount = 0;
  int linecount = 1;
  SolidBrush hbBkBrush = new SolidBrush(m_crBackColor);
  //Fill control rectangle 
  _buff.FillRectangle(hbBkBrush,m_rect);
  //Initialize two rectangeles
  Rectangle clipDstn = Rectangle.Empty;
  Rectangle clipSrc = Rectangle.Empty;

  //Now we will start main processing.
  for (int ix = 0; ix < strlen; ix++)
  {
    //This method calculates clip region for current char.
    GetCharBmpOffset((char)m_StrText[ix], ref clipSrc);
    //Initializes target clip.
    clipDstn = new Rectangle(x,y,clipSrc.Width,clipSrc.Height);
    //Draw current symbol in buffer
    _buff.DrawImage(m_ImageMatrix, clipDstn, clipSrc.X, 
              clipSrc.Y, clipSrc.Width, clipSrc.Height, 
              GraphicsUnit.Pixel, bmpAttr);

    x += m_CharWidth + m_XSpacing;
    charcount++;
    if ((charcount == m_MaxXChars) && m_MaxYChars == 1)
    {
      break;
    }
    else if ((charcount == m_MaxXChars) && m_MaxYChars > 1)
    {
      if (linecount == m_MaxYChars)
      {
        break;
      }
      x = charcount = 0;
      y += m_CharHeight + m_YSpacing;
      linecount++;
    }
  }
  //And finally draw our image on control surface.
  pea.Graphics.DrawImage(_buffImage,0,0); 
  //Next lines are necessary...
  hbBkBrush.Dispose();
  hbBkBrush= null;
  bmpAttr.Dispose();
  bmpAttr = null;
  _buff.Dispose();_buff = null;

  _buffImage.Dispose(); _buffImage = null;
}

Conclusion and current issues

The control works perfect, without flickering, but, if you will use the control without scrolling. If you will need scrolling, your application will consume 100% CPU!!!.

Probably, the following line causes the strong consumption of CPU time:

...

//Draw current symbol in buffer 
_buff.DrawImage(m_ImageMatrix, clipDstn, clipSrc.X, 
          clipSrc.Y, clipSrc.Width, clipSrc.Height, 
          GraphicsUnit.Pixel, bmpAttr);
...

It's really so... if you comment out this line, you will get 0% CPU usage.

Conclusion

For heavy operations, it is better to use native methods of API. You may try replacing this line with another one, and try using the API method:

[System.Runtime.InteropServices.DllImportAttribute("gdi32.dll")]
private static extern bool BitBlt(
IntPtr hdcDest, // handle to destination DC
int nXDest, // x-coord of dest upper-left corner
int nYDest, // y-coord of dest upper-left corner
int nWidth, // width of destination rectangle
int nHeight, // height of destination rectangle
IntPtr hdcSrc, // handle to source DC
int nXSrc, // x-coord of source upper-left corner
int nYSrc, // y-coord of source upper-left corner
System.Int32 dwRop // raster operation code
);