Hey,

I've been working with brightness thresholding, trying to make an installation where users can 'draw' with light onto a mirrored projection of themselves. I have the drawing part down, but I can't seem to make the captured video of the user visible.
Any suggestions?!

Heres the code so far:
*best tested in a darker room using a small light source ( tiny flash light, glow stick etc..)
import processing.video.*;

color black = color(0,2);
color white = color(255,0,125);
int numPixels;
Capture video;

void setup() {
 size(640, 480); // Change size to 320 x 240 if too slow at 640 x 480
 strokeWeight(5);
 // Uses the default video input, see the reference if this causes an error
 video = new Capture(this, width, height, 24);
 numPixels = video.width * video.height;
 noCursor();
 smooth();
}

void draw() {
 if (video.available()) {
   video.read();
     //image(video, 0, 0);
   video.loadPixels();
   int threshold = 240; // Set the threshold value
   float pixelBrightness; // Declare variable to store a pixel's color
   // Turn each pixel in the video frame black or white depending on its brightness
   loadPixels();
   for (int i = 0; i < numPixels; i++) {
     pixelBrightness = brightness(video.pixels[i]);
     if (pixelBrightness > threshold) { // If the pixel is brighter than the
       pixels[i] = white; // threshold value, make it white
     }
     else { // Otherwise,
     pixels[i] = black;
     //  pixels[i] = video.pixels[i]; // make it black
     }
   }
   updatePixels();
   // Test a location to see where it is contained. Fetch the pixel at the test
   // location (the cursor), and compute its brightness
   int testValue = get(mouseX, mouseY);
   float testBrightness = brightness(testValue);
   if (testBrightness > threshold) { // If the test location is brighter than
     fill(black); // the threshold set the fill to black
   }
   else { // Otherwise,
     fill(white); // set the fill to white
   }
 
 }
}

I am doing a similar project and am having a similar problem. I am making a sketch that will allow the user to 'draw' via moving their body in view of a webcam.
I am overlaying the brightness threshold capture over a live video feed so the user can see themselves. The brightness threshold feed leaves a trail after movement so the user is 'drawing'. So far so good. However, the live feed is also leaving a trail which I do not want to happen.
Originally I did which is why the code is there but now when I take out the showImage.blend(...)..., the live feed stops showing up on the screen. I have tried changing the filter and interchanging the various video feeds but nothing doing. Either the live feed disappears completely or it leaves a trail.

Here's the code -

//----- brightness threshold adapted from Processing Learning Tutorials
//----- http://processing.org/learning/libraries/brightnessthresholding.html
//----- by Golan Levin


import processing.video.*;

color black = color(0,1);
color white = color(255);
int numPixels;

Capture video;

PImage liveFeed; //live feed from webcam
PImage showImage; //needed to display feed to user
//PImage = Datatype for storing images. Processing can display .gif, .jpg, .tga, and .png images.
//using this means we can export out images of what's on screen so the trail will be visible unlike in movie classes


void setup() {
 size(800,600);
 strokeWeight(5);
 video = new Capture(this, width, height, 30); //width, height, frameRate
 liveFeed = createImage(width, height, RGB);  //width/height = defined in SIZE
 showImage = createImage(width, height, RGB); //need RGB to define as a PImage and not image
 
 numPixels = video.width * video.height;
 noCursor();
 smooth();
}

void draw() {
   frameRate(30);
   if (video.available()) {
     video.read();
     video.loadPixels();
       
     //-----flip video feed AND IT WORKS!!!
     
     int increment = 0;
     
     for (int y = 0; y < video.height; y++) {
       for (int x = video.width - 1; x >= 0 ; x--) {
         liveFeed.pixels[increment] = video.pixels[y*width + x];
         increment++;
       }
     }    
   
     //-----threshold
   
   
   int threshold = 200; // Set the threshold value
   float pixelBrightness; // Declare variable to store a pixel's color
   // Turn each pixel in the video frame black or white depending on its brightness
   loadPixels();
   for (int i = 0; i < numPixels; i++) {
     pixelBrightness = brightness(liveFeed.pixels[i]);
     if (pixelBrightness > threshold) { // If the pixel is brighter than the
       pixels[i] = white;               // threshold value, make it white
     }
     else { // Otherwise,
       pixels[i] = black; // make it black
     }
   }
   
   updatePixels();
   
     //displays image on screen
     tint(255,20);//alpha of showImage
     image(showImage, 0, 0); //image, x co-ord, y co-ord

     //showImage.filter(GRAY); //other filters still don't make it appear!!!
     showImage.blend(liveFeed, 0, 0, width, height, 0, 0, width, height, LIGHTEST);
//swapping liveFeed, showImage & video doesn't work!!!
     //(src image,x,y,width,height,x co-ord destinations upper left corner,y co=ord destinations upper left corner, MODE)
     //Copies a pixel or rectangle of pixels using different blending modes
     
   }//end o video available

}//end o draw


Any help would be greatly appreciated!