how can I solve this problem ? they ask me that the var ctx is unavailable class

so0ofy

var ctx;

PImage currentImage;
PImage previousImage;
final int cameraWidth = 960;
final int cameraHeight = 640;
final int shrinkFactor = 8;               // sort of arbitary, the amount the image will be shrunk for for motion detection
final float colorChangeThreshold = 50.0;  // again arbitary, the "amount" of color a pixel needs to change to be regarded as motion 

void setup() { 
    size(960,640);
    ctx = externals.context;    
}

void draw() {
    if (!video.available) return;

    // I want 2 images in memory, the current and previous image and the differences between these two things is motion!
    previousImage = currentImage;  

    pushMatrix();
    translate(width,0);
    scale(-1,1);                                            //mirror the video so it is like looking in a mirror
    ctx.drawImage(video, 0, 0, cameraWidth, cameraHeight);  //video is defined outside processing code
    popMatrix();

    currentImage=get(0,0,cameraWidth,cameraHeight);

    PImage motionDetectionImage = createImage(cameraWidth/shrinkFactor, cameraHeight/shrinkFactor, RGB);
    if (currentImage != null && previousImage != null) {    
        j = 0;
        for (int i = 0 ; i <  previousImage.pixels.length; i=nextI(i)) {
           color p1 = previousImage.pixels[i];
           color p2 = currentImage.pixels[i];

           float totalDiff =  abs(red(p1) - red(p2)) + abs( green(p1) - green(p2)) + abs(blue(p1) - blue(p2));

           if (totalDiff > colorChangeThreshold) { 
             motionDetectionImage.pixels[j] = color(255);
           } else {
             motionDetectionImage.pixels[j] = color(0);
           }           
           j = j + 1;
        }
        image(motionDetectionImage, 0, 0);
    }
}

private int nextI(int i) {
  if ( (int)( (int)(i+shrinkFactor) / (int)(cameraWidth) ) % (int) shrinkFactor == 0){
    return i + shrinkFactor;
  } else {
    return i + shrinkFactor + cameraWidth % shrinkFactor + (cameraWidth*(shrinkFactor-1));
  }
}

Ater

If you write in java, you do not use "var", but rather particular data type (which corresponds to the class you want to use, something like ExternalContext ctx;. When you do this ctx = externals.context; what do you expect ctx to be?

so0ofy

ctx is meant context .. How can I change it ? do you have any suggestions

Ater

Where did you see examples or guidance, which your program is based on? I see it has something to do with motion detection, but can't understand the logic..

Context may mean different things in web or mobile applications..

so0ofy

yeah it has motion detection and using webcam .. you can see the example in this link : https://github.com/ACassells/processing.js.SimpleWebCamInteraction/blob/master/SimpleMotionDetectionWebcamInteractionImage/SimpleMotionDetectionWebcamInteractionImage.pde

so0ofy

So I want to make an installation with like falling objects (circles or flowers) and people can interact with by hand movement .. how it is possible ? if you have ant easier way for doing that

Ater

So, this is javascript... Processing.js is not evolving anymore, I believe, and I never used it, really. There's a lot of libraries to do it in java mode. Do you want this to be in javascript cause you want it for a web? I don't know much on the topic to help you make this work, but maybe you can find alternative solutions on what you want to do?

so0ofy

simliar like this

I still want to use processing 3 and webcam to create an installtion