Use a value within pushMatrix () and popMatrix () outside it

Apoel_95

Hi, I would like to use a value created within pushMatrix () and popMatrix (), outside this block. In my case, I would use the value generated by l = faces [0] .x; In rect outside pushMatrix () and popMatrix (). How can I do?

TfGuy44

if(faces.length>0){ l = screenX( faces[0].x, faces[0].y ); }

https://processing.org/reference/screenX_.html

koogs

We can't debug pictures of code.

The value of l outside the push / pop is identical to that inside. What changes is the projection because of the scale and translate.

Your for loop is useless btw, why are you accessing the 1st item multiple times?

Apoel_95

Because I want to recognize only the first face she sees.

How do I use translated and climbed value outside of push / pop?

This is my code:

import processing.video.*;
import gab.opencv.*;
import java.awt.Rectangle;

Capture cam;
OpenCV opencv;
int l;
void setup() {
  size(640, 480);

  cam = new Capture(this, width, height, 30);
  opencv = new OpenCV(this, width, height);
  opencv.loadCascade(OpenCV.CASCADE_FRONTALFACE);  
  cam.start();
}

void draw() {
  if (cam.available() == true) {
    cam.read();
  }

  pushMatrix();
  scale(-1, 1);
  translate(-cam.width, 0);
  image(cam, 0, 0); 

  opencv.loadImage(cam);
  Rectangle[] faces = opencv.detect();

  noFill();
  stroke(0, 255, 0);
  strokeWeight(3);
  for (int i = 0; i < faces.length; i++) {
    rect(faces[0].x, faces[0].y, faces[0].width, faces[0].height);
    l = screenX( faces[0].x ,);
  }
  println(l);

  popMatrix(); 

  rect(l,0,50,50);
}

Chrisir

TfGuy44 explained it

Apoel_95

l = screenX( faces[0].x );

It does not work, it says I must add another value. What should I put?

koogs

Because I want to recognize only the first face she sees.

then you don't need the loop.

Apoel_95

then you don't need the loop. How do I do it?

koogs

rect(faces[0].x, faces[0].y, faces[0].width, faces[0].height);

is enough, no need for a loop.

you need to use the y position for the other variable, even if you only want the result for x.

l = screenX(faces[0].x, faces[0].y);

Apoel_95

l = screenX(faces[0].x, faces[0].y);

Ok for that I solved

rect(faces[0].x, faces[0].y, faces[0].width, faces[0].height);

For this, without the cycle, it does not work

koogs

please examine that picture. can you read it? no. neither can we.

what happens when the camera doesn't detect any faces?

well, then this will return an empty Rectangle array

Rectangle[] faces = opencv.detect();

but in this bit of code

rect(faces[0].x, faces[0].y, faces[0].width, faces[0].height);

it's accessing the first element regardless of whether it exists or not. that's the error.

the easy way around it to is check the length of the array before trying to access it.

if (faces.length > 0) {
  // it's safe to use the array
  rect(faces[0].x, faces[0].y, faces[0].width, faces[0].height);
}

Apoel_95

I solved, thank you so much for your help