Comparing current angle of tracked pixel to previous, delay?

hen

Hi,

I am having an issue with comparing points, current and previous. In my current sketch the angles compared are updated so frequently that the difference is minimal.

    if ((closestX>320)&&(closestY<240)) {  //Square 4
      tempX = closestX-320;
      tempY = closestY;
      currentAngle = degrees (atan(tempY/tempX));


      tempAngle = currentAngle - previousAngle;


      println("current angle is :" + currentAngle);
      println("previous angle is:" + previousAngle);
      println("difference is:" + tempAngle);


      previousAngle = (currentAngle);
    }
  }
}

Is there a way to compare angle of half a second ago to the current angle?

hen

full sketch:

import processing.video.*;

float tempX;  //temporal x value for trigonometry 
float tempY;  //temporal y value for trigonometry 
float tempAngle; // //temporal angle value for trigonometry 
float currentAngle=0;
float previousAngle=0;

// Variable for capture device
Capture video;


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

void setup() {
  size(640, 480);
  video = new Capture(this, width, height);
  video.start();
  // 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);
  pushMatrix();
  scale(-1, 1);
  image(video.get(), -width, 0);
  popMatrix();

  // 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(4.0);
    stroke(0);
    ellipse(closestX, closestY, 40, 40);


    if ((closestX<320)&&(closestY<240)) {   // Square 1
      println("SQ1");
    }
    if ((closestX<320)&&(closestY>240)) {  //Square 2
      println("SQ2");
    }
    if ((closestX>320)&&(closestY>240)) {  //Square 3
      println("SQ3");
    }
    if ((closestX>320)&&(closestY<240)) {  //Square 4
      tempX = closestX-320;
      tempY = closestY;
      currentAngle = degrees (atan(tempY/tempX));


      tempAngle = currentAngle - previousAngle;


      println("current angle is :" + currentAngle);
      println("previous angle is:" + previousAngle);
      println("difference is:" + tempAngle);


      previousAngle = (currentAngle);
    }
  }
}

void mousePressed() {

  // Save color where the mouse is clicked in trackColor variable
  int x = video.width - mouseX;
  int y = mouseY;
  int loc = y*video.width+x;
  trackColor = video.pixels[loc];
}

PhiLho

If you need to keep track of angles over a period of time, store them in an array.

Use millis() to keep track of time.

hen

Sorry I am really new to processing and I am struggling to understand how to use array, I understand that array will create a list of my previous angles and these can be accessed according to a millis() condition. Could you give me an example?

Thanks.

GoToLoop

If you know how many angles you're gonna need, use a float[]:
http://processing.org/reference/Array.html

Otherwise, use a FloatList:
http://processing.org/reference/FloatList.html

hen

I know that I want to compare the current angle with the angle that was like 0.5 seconds ago