[Team3266Spencer]

Originally Posted by Justin m

What the you have to do is determine the width of the target in pixels, given a constant value w/ the target centered, and find the hypotenuse, which is your distance
EDIT: Use the height for distance, not the width.The width can vary with angle to the target.
Example:
Note, these are necessary constants

    public static final int IMAGE_WIDTH = 320;
    public static final int IMAGE_HEIGHT = 240;
    public static final double TARGET_WIDTH = 2.0;
    public static final double TARGET_HEIGHT = 1.5;
    public static final double RECTANGLE_QUALITY_THRESHOLD = 95.0;
    public static final double PARTICLE_TO_IMAGE_THRESHOLD = 0.05;
    public static final double PARTICLE_AREA_THRESHOLD = 250.0;
    protected double fieldOfViewWidth = 0.0;

    /**
     * Return distance to target in inches
     *
     * @param targetHeightInPixels
     * @return
     */
    public double GetDistanceToTarget(int targetHeightInPixels)
    {
        double fieldOfViewHeight = TARGET_HEIGHT / targetHeightInPixels * IMAGE_HEIGHT;
        distance = (fieldOfViewHeight / 2.0) / 
                /*
                 * tan 23.5 degrees
                 */
                  0.4348123749;
        return distance * 12.0 * 1.4;
    }

I am assuming you can figure out how to filter for targets.

However the height varies as well depending on the height of your robot and how close you are to the target.