does anybod know how to access pixel data?

Hi,

While this reply is late I thought best to include the answer in case any other fall across this question.

Lets assume you have read your image in as a colour image:

Image<bgr,Byte> My_Image = new Image<bgr,Byte>("filename_string");

To access each individual pixel of My_Image you call the .Data property but lets not forget that a Bgr image has 3 matrices representing Red, Green, Blue

//Red
byte Red_val = My_Image.Data[y,x,0];
//Green
byte Green_val = My_Image.Data[y,x,1];
//Blue
byte Blue_val = My_Image.Data[y,x,2];

Now to check if this pixel is white "Red_Val", "Green_val" and "Blue_Val" will be equal to 255.

Now to set a pixel to a colour EMGU has made the method slighter simpler then setting the red green and blue spectrum's individually you can simply use:

My_Image[i,j] = new Bgr(Color.Red);

Now if you are using greyscale images you obviously can't assign the colour red but its worth noting that for this image type there is only 1 matrix representing it's values therefore to access its data you would use:

//Greyscale
byte Gray_val = My_Image.Data[y,x,0];

So putting it all together you would be after something like this:

Timer timer = new Timer();
Image<bgr,byte> My_Image;
Image<bgr,byte> My_Image_todrawon;
Random xy_rand =  new Random();

public FormWithTimer()
{
    InitializeComponent();

    My_Image = new Image<bgr,byte>("filename_string");
    
    timer.Tick += new EventHandler(timer_Tick); // Everytime timer ticks, timer_Tick will be called
    timer.Interval = (3000);              // Timer will tick every 3 seconds
    timer.Enabled = true;                       // Enable the timer
    timer.Start();                              // Start the timer (Make sure your Images area assigned before you start this);


}

void timer_Tick(object sender, EventArgs e)
{
    //Clear all your positions by makeing a copy image to draw on else your change 
    //will be permanent until you read the image in again
    My_Image_todrawon = My_Image.Copy();

    for(int i = 0; i< 300; i++)
    {
        int ran_x_pos = xy_rand.Next(My_Image.Width);
        int ran_y_pos = xy_rand.Next(My_Image.Height); //limit there values to within image boundaries

        byte Red_val = My_Image.Data[ran_y_pos,ran_x_pos,0];
        //Green
        byte Green_val = My_Image.Data[ran_y_pos,ran_x_pos,1];
        //Blue
        byte Blue_val = My_Image.Data[ran_y_pos,ran_x_pos,2];
        
        if(Red_val == 255 && Green_val == 255 && Blue_val == 255) //See if White
        {
            //Mark the position within the image in red
            My_Image[i,j] = new Bgr(Color.Red);
            
            //Do any other operations such as record position assign values etc
        }

    }
}

This should help get you started in whatever you application may be.

Cheers
Chris