First time posting, and haven't been using Processing for too long. Long story short; I'm trying to take in live video and find and track an area of the video image that is closest in color value to a specified color.

The use will be for a line tracking bot: the camera will be pointed directly at the ground ahead of the bot. I wish for processing to track the line (and thereby steer the bot). I want it to pick up on the color of the line, and not just the line itself because I will eventually want intersections and many lines of different colors for different bots.

I have attempted to modify the BrightnessTracking example included with the software. Below is a copy of my code.

Does anyone have any tips or tricks, or can see an error in my code?

//begin code

import processing.video.*;

Capture video;

void setup() {
 size(640, 480); // Change size to 320 x 240 if too slow at 640 x 480
 // Uses the default video input, see the reference if this causes an error
 video = new Capture(this, width, height, 30);
 noStroke();
 smooth();
 int colors=color(54,255,0); //we define the color that we want the bot to track.
}

void draw() {
 if (video.available()) {
   video.read();
   image(video, 0, 0, width, height); // Draw the webcam video onto the screen
   int brightestX = 0; // X-coordinate of the brightest video pixel
   int brightestY = 0; // Y-coordinate of the brightest video pixel
   float brightestValue = 0; // Brightness of the brightest video pixel
   // Search for the brightest pixel: For each row of pixels in the video image and
   // for each pixel in the yth row, compute each pixel's index in the video
   video.loadPixels();
   int index = 0;
     for (int x = 0; x < video.width; x++) {
       int y=height/2;
       // Get the color stored in the pixel
       int pixelValue = video.pixels[index];
       // Determine the brightness of the pixel
       float pixelBrightness = color(pixelValue);
       // If that value is brighter than any previous, then store the
       // brightness of that pixel, as well as its (x,y) location
       if (abs(pixelValue-colors)) > (abs(brightestValue-colors)) {
         brightestValue = pixelBrightness;
         brightestY = y;
         brightestX = x;
       }
       index++;
     }
   // Draw a large, yellow circle at the brightest pixel
   fill(54, 255, 0, 300);
   ellipse(brightestX, brightestY, 100, 100);
 }
}

Hey Paul, thanks for your help. I now have working code. Currently, I have it set to track green (RGB,0,255,0). Below is the code. However, there are some major problems in design, but I will work on those later. But anyway, it works for now. Check it out and let me know what you think.

/**
* Color Tracking
* by Justin Brooks
*
*
* based on original code:
*   Brightness Tracking
*   by Golan Levin.
*
* Tracks the tracks pixel closest in color to specified color.
*/


import processing.video.*;

Capture video;

void setup() {
 size(640, 480); // Change size to 320 x 240 if too slow at 640 x 480
 // Uses the default video input, see the reference if this causes an error
 video = new Capture(this, width, height, 30);
 noStroke();
 smooth();
}

void draw() {
 if (video.available()) {
   video.read();
   image(video, 0, 0, width, height); // Draw the webcam video onto the screen
   int colorX = 0; // X-coordinate of the closest in color video pixel
   int colorY = 0; // Y-coordinate of the closest in color video pixel
   float closestColor = 10000; //we set this to be abritrarily large, once program runs, the first pixel it scans will be set to this value
   // Search for the closest in color pixel: For each row of pixels in the video image and
   // for each pixel in the yth row, compute each pixel's index in the video
   video.loadPixels();
   int index = 0;
   for (int y = 0; y < video.height; y++) {
     for (int x = 0; x < video.width; x++) {
       // Get the color stored in the pixel
       color pixelValue = video.pixels[index];
       // Determine the color of the pixel
       float colorProximity = abs(red(pixelValue)-0)+abs(green(pixelValue)-255)+abs(blue(pixelValue)-0);
       // If that value is closer in color value than any previous, then store the
       // color proximity of that pixel, as well as its (x,y) location
       if (colorProximity < closestColor) {
         closestColor = colorProximity;
         closestColor=closestColor-10; //thoguht behind this is that it once it "locks" on to an object of color, it wont let go unless something a good bit better (closer in color) comes along
         colorY = y;
         colorX = x;
       }
       index++;
     }
   }
   // Draw a large, yellow circle at the brightest pixel
   fill(255, 204, 0, 128);
   ellipse(colorX, colorY, 200, 200);
 }
}