How to transfer color images to grey images using C#

How to transfer color images to grey images using C#

• kjehed

  Better yet, since human eyes have different sensitivities to R,G,B light, the following matrix gives you are more "natural" transform

  float[][] matrix =

  {

  new float[] {0.299f, 0.299f, 0.299f, 0, 0},

  new float[] {0.587f, 0.587f, 0.587f, 0, 0},

  new float[] {0.114f, 0.114f, 0.114f, 0, 0},

  new float[] {0, 0, 0, 1, 0},

  new float[] {0, 0, 0, 0, 1}

  };

  
  
  

• Darkside

  Thanks a lot for you guys' suggestions.
  
  

• Santhosh Pallikara

  Hi, FugersonHall

  Use colorMatrix to gray the image can be the efficient way.

  Hope it helps.

  Thanks

  
  
  

• Cory Cundy

  Average the R,G,B values of your image

  newColor.R = (oldColor.R + oldColor.G + oldColor.B) / 3;

  newColor.G = (oldColor.R + oldColor.G + oldColor.B) / 3;

  newColor.B = (oldColor.R + oldColor.G + oldColor.B) / 3;

   

  Bitmap bp = new Bitmap("c:\\test.jpg");

  for (int i = 0; i < bp.Height; i++)

  for (int j = 0; j < bp.Width; j++)

  {

  Color oldColor = bp.GetPixel(j, i);

  int newColor = (oldColor.R + oldColor.G + oldColor.B)/3;

  bp.SetPixel(j, i, Color.FromArgb(newColor, newColor, newColor));

  }

  However this is a pixel-by-pixel method, which is slow. Maybe you can change image attribute to change to Grayscale pictures....

  
  
  

• InfiniZac

  And yet one more greyscale matrix; this one happens to be the one .NET uses to convert a colored object to the 'disabled' color:
  
  

  float[][] matrix =

  {

  new float[] {0.2125f, 0.2125f, 0.2125f, 0, 0},

  new float[] {0.2577f, 0.2577f, 0.2577f, 0, 0},

  new float[] {0.0361f, 00361f, 0.0361f, 0, 0},

  new float[] {0, 0, 0, 1, 0},

  new float[] {0.38f, 0.38f, 0.38f, 0, 1}

  };

  
  
  
  

• meoryou

  Thanks a lot for your so quick response. The performance is very key for this project. Will "change image attribute to change to Grayscale pictures" be fast Any other ideas or other sample codes Thanks a lot again.
  
  

• GregRoberts

  How about this

  Image img = new Bitmap("c:\\test.jpg");

  ImageAttributes attr = new ImageAttributes();

  float[][] matrix =

  {

  new float[] {0.5f, 0.5f, 0.5f, 0, 0},

  new float[] {0.5f, 0.5f, 0.5f, 0, 0},

  new float[] {0.5f, 0.5f, 0.5f, 0, 0},

  new float[] {0, 0, 0, 1, 0},

  new float[] {0, 0, 0, 0, 1}

  };

  ColorMatrix cm = new ColorMatrix(matrix);

  attr.SetColorMatrix(cm, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);

  Graphics g = Graphics.FromImage(img);

  g.DrawImage(img, new Rectangle(0, 0, img.Width, img.Height), 0, 0, img.Width, img.Height, GraphicsUnit.Pixel, attr);

  img.Save("c:\\test2.jpg");

  g.Dispose();

  
  
  
• How to transfer color images to grey images using C#