protip: it would be easier to help with your code if you actually posted it.

This is the code I have found and altered a bit, it tracks a color but doesn't create lines to form letters... Could anyone help?

Thanks a lot a lot a lot!

- Anna Clara


import processing.video.*;

// Variable for capture device
Capture video;

// A variable for the color we are searching for.
color trackColor;

void setup() {
  size(720,640);
  video = new Capture(this,width,height,15);
  // Start off tracking for red
  trackColor = color(255,0,0);
  smooth();
}

void draw() {
  // Capture and display the video
  if (video.available()) {
    video.read();
  }
  video.loadPixels();
  image(video,0,0);

  // Before we begin searching, the "world record" for closest color is set to a high number that is easy for the first pixel to beat.
  float worldRecord = 500;

  // XY coordinate of closest color
  int closestX = 0;
  int closestY = 0;

  // Begin loop to walk through every pixel
  for (int x = 0; x < video.width; x ++ ) {
    for (int y = 0; y < video.height; y ++ ) {
      int loc = x + y*video.width;
      // What is current color
      color currentColor = video.pixels[loc];
      float r1 = red(currentColor);
      float g1 = green(currentColor);
      float b1 = blue(currentColor);
      float r2 = red(trackColor);
      float g2 = green(trackColor);
      float b2 = blue(trackColor);

      // Using euclidean distance to compare colors
      float d = dist(r1,g1,b1,r2,g2,b2); // We are using the dist( ) function to compare the current color with the color we are tracking.

      // If current color is more similar to tracked color than
      // closest color, save current location and current difference
      if (d < worldRecord) {
        worldRecord = d;
        closestX = x;
        closestY = y;
      }
    }
  }

  // We only consider the color found if its color distance is less than 10.
  // This threshold of 10 is arbitrary and you can adjust this number depending on how accurate you require the tracking to be.
  if (worldRecord < 10) {
    // Draw a circle at the tracked pixel
    fill(trackColor);
    strokeWeight(0.0);
    stroke(0);
    ellipse(closestX,closestY,18,18);
  }
}

void mousePressed() {
  // Save color where the mouse is clicked in trackColor variable
  int loc = mouseX + mouseY*video.width;
  trackColor = video.pixels[loc];
}

The problem is that when you update the screen with:

image(video,0,0);

...you cover over the previously drawn circle.  The solution is to draw the circle to a transparent buffer image and draw this image on top of the video.  The buffer image will store all the previously drawn circles and create the line effect you're after.

To create a buffer image see createGraphics()

Do you want this ?