Hello

I'm trying to get in touch with Charles Forman, or one of the other fellows on Setpixel.com that has done some video tracking / manipulation with particles.

I would greatly appreciate any help or leads.
Thanks

Well I'm looking to use an iSight to track motion or outline a person standing in front of it. Then I would like to translate that motion or silhouette into a particle generator, and lastly connect up some serial stuff to control the particles.

I'm cool with serial, and pretty good with particles, but a little iffy on the tracking. I'm guessing it's just comparing an array of pixels to the last one and calculating the change, but I would love to see exactly what's going on.

Heres some code I wrote that compares a video capture frame to the previous and calculates the difference maybe this can help you


import processing.opengl.*;

import processing.video.*;
Capture myCapture;

PImage img;
PImage lastcap;




void setup() {
 size(600, 600,P3D);
// println(1/4);
  println(Capture.list());
 String s = "Logitech QuickCam Pro 4000-WDM";
 myCapture = new Capture(this, s, 200, 200, 30);
 //template is a 200x200 black image;
 img=loadImage("template2.jpg");
 img.format=ARGB;
 lastcap=loadImage("template2.jpg");


}




void draw() {
background(0);
lastcap.copy(myCapture, 0, 0, myCapture.width, myCapture.height, 0, 0, myCapture.width, myCapture.height);

 if(myCapture.available()) {
   // Reads the new frame
   myCapture.read();
 }

findchange();
   


   image(img, 0, 0, width, height);

}



void findchange(){
img.loadPixels();
for (int i=0; i<myCapture.pixels.length; i++){
//int colordiff=abs(int(brightness(lastcap.pixels[i]))-int(brightness(myCapture.pixels[i])));

int bluediff=abs((lastcap.pixels[i]&0xFF)-(myCapture.pixels[i]&0xFF));
int greendiff=abs(((lastcap.pixels[i]>>8)&0xFF)-((myCapture.pixels[i]>>8)&0xFF));
int reddiff=abs(((lastcap.pixels[i]>>16)&0xFF)-((myCapture.pixels[i]>>16)&0xFF));

//if (colordiff > 0){
img.pixels[i]=(220<<24)+(reddiff<<16)+(greendiff<<8)+bluediff;
//}
}
img.updatePixels();
}

Thanks st33d
This looks interesting although I think it produces a differnt effect than the code I posted. I didnt know what XOR was and looked it up, from what I could understand it dosn't calculate difference. I took the code you posted and had to mess with it a little so the alpha channel wouldnt get messed up. I wonder is there a way to use bitwise operators to get difference, am I misunderstanding the XOR?


void imgDif(){
img.loadPixels();
  for (int i=0; i<img.pixels.length;i++){
  img.pixels[i]=(255<<24)+((myCapture.pixels[i]&0xFFFFFF)^(lastcap.pixels[i]&0xFFFFFF));
 
  }
img.updatePixels();
}

Im using OpenGL because of the performance boost, especially when using larger display windows. I als0 like the way it scales up images. Since analyzing 600*600 pixels is way to much for my computer, I can bring in a 200*200 image from the cam and it won't look pixelated when I diplay it at 600*600.

Dylan or anyone, can you explain this function a bit more?

Code:

void findchange(){ 
img.loadPixels(); 
for (int i=0; i<myCapture.pixels.length; i++){ 
//int colordiff=abs(int(brightness(lastcap.pixels[i]))-int(brightness(myCapture.pixels[i]))); 
 
int bluediff=abs((lastcap.pixels[i]&0xFF)-(myCapture.pixels[i]&0xFF)); 
int greendiff=abs(((lastcap.pixels[i]>>8)&0xFF)-((myCapture.pixels[i]>>8)&0xFF)); 
int reddiff=abs(((lastcap.pixels[i]>>16)&0xFF)-((myCapture.pixels[i]>>16)&0xFF)); 
 
//if (colordiff > 0){ 
img.pixels[i]=(220<<24)+(reddiff<<16)+(greendiff<<8)+bluediff; 
//} 
} 
img.updatePixels(); 
} 
  

Basically this is creating that halo around the moving images if I gather correctly. What does << do? and &0xFF is Hex colors? or what?

related to this topic(track pixel change), i'm trying to create an image that captures a complete movement.(much like http://www.phantasian.com/timescape/timescape.htm )

however what i need is the image to record the scene once and then after that only the changing pixels, leaving a residue of the movement.

i'm a complete novice at processing and don't even know where to start...this is in aide of a pre-study for a spatial project.

any help is much appreciated...

thanks
riaan