CODEWITHSUNDEEP
c#.netwinforms
BigBug
BigBug

Reputation: 6290

Photo to grayscale in C#.NET and Windows Forms

How do I make this into a grayscale?

After much googling it seems the best I can do is change the tint of the picture (in the code bellow, it's a green tint). How can I do it?

byte[] redGreenBlueVal = new byte[numBytes];

for (int i = 0; i < redGreenBlueVal .Length; i += 4)
{
    redGreenBlueVal [i + 0] = (byte)(.114 * redGreenBlueVal [i + 0]); --> blue
    redGreenBlueVal [i + 1] = (byte)(.587 * redGreenBlueVal [i + 1]); --> green
    redGreenBlueVal [i + 2] = (byte)(.299 * redGreenBlueVal [i + 2]); --> red
}

Upvotes: 0

Views: 472

Answers (3)

John Carter
John Carter

Reputation: 2056

In effect you're adjusting HSB so this should get you a better grayscale image: 30% RED 59% GREEN 11% BLUE

byte[] redGreenBlueVal = new byte[numBytes];

for (int i = 0; i < redGreenBlueVal .Length; i += 4)
{
      gray = (byte)(.11 * redGreenBlueVal [i + 0]);
      gray += (byte)(.59 * redGreenBlueVal [i + 1]); 
      gray += (byte)(.3 * redGreenBlueVal [i + 2]);

      redGreenBlueVal [i + 0] = gray;
      redGreenBlueVal [i + 1] = gray;
      redGreenBlueVal [i + 2] = gray;

}

Upvotes: 2

Tibi
Tibi

Reputation: 3875

To get a grayscale image, the basic idea is to have all the 3 channels hold the same value. There are many ways to do this, the simplest ones are:

  • use only one of the channels (it will look like when you select individual channels in photoshop)
  • calculate an average of the 3 channels

Upvotes: 0

Ryan
Ryan

Reputation: 19

You could try setting each pixels colour channels to the average value for that pixel.

i.e.

for( int i = 0; i < redGreenBlueVal.Length; += 4 )
{
    int average = (redGreenBlueVal[i + 0] + redGreenBlueVal[i + 1] + redGreenBlueVal[i + 2])/3;
    redGreenBlueVal[i + 0] = average;
    redGreenBlueVal[i + 1] = average;
    redGreenBlueVal[i + 2] = average;
}

Upvotes: 1

Related Questions