How to import the Blob class?

Processing Libraries
1

Apologies for what is probably a painfully basic question. I’m new to Processing, but I’m not new to media programming (19+ year user of SuperCollider, 2-3 years teaching with Pure Data). Processing 3.5.4.

I am seeing a number of code examples online using the Blob class. (The goal is to supplement some image processing in Pure Data with blobby goodness – Pd’s Gem external claims to have a blob tracker but it’s slow enough to be unusable. That’s fine because Pd focuses on audio rather than video processing – so the lesson for the students will be how to integrate with other tools that are better suited to the task.)

Trying it for myself, I got as far as opening and displaying the camera :+1: and instantiating an OpenCV object :+1: but it chokes on ‘Cannot find a class or type named “Blob”’.

I tried several Google searches about “processing language Blob class” and I find many, many pages about how to use Blob, but nothing about where it’s defined. I can’t even find a reference for the class.

Then I noticed that these code examples all(?) import hypermedia.video.*;.

Processing IDE → Import Library → Add Library → search “hyper” oh, well, there’s nothing. Search “video” and several packages do show up, but there is no indication in the window which one of those might be hypermedia.

I also see that there is a BlobDetection library, but I’m not sure this is the right one because I didn’t see import blobDetection.*; in any of the examples (and blobs comes from the OpenCV object anyway).

So… this incoming user is experiencing a disconnect between examples and documentation.

Where do I get Blob?

hjh

Working example, displaying camera:

import processing.video.*;

Capture video;

void setup() {
  size(640, 480);
  video = new Capture(this, 640, 480);
  video.start();
}

void draw() {
  if (video.available() == true) {
    video.read();
  };
  image(video, 0, 0);
}

This sketch can’t find Blob:

import gab.opencv.*;
import processing.video.*;

OpenCV opencv;
Capture video;

float s=10;
float sc;

void setup() {
  size(640, 480);
  video = new Capture(this, 640, 480);
  opencv=new OpenCV(this, 640, 480);
  video.start();
}

void draw() {
  if (video.available() == true) {
    video.read();
  };
  image(video, 0, 0);
  // background(255);
  opencv.threshold(80);
  Blob[] blobs=opencv.blobs(10, width*height,100,true,OpenCV.MAX_VERTICES*4);
  for(int i=0; i<blobs.length;i++) {
    for(int j=0; j<blobs[i].points.length; j++) {
      fill(255);
      stroke(sc);
      rect(blobs[i].points[j].x,blobs[i].points[j].y,s,s);
    }
  }
}
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2

So this morning I thought, why not import blobDetection and see what happens?

I expected some incompatibility with the Blob interface, but instead found that OpenCV was the problem:

“The function blobs(int, int, int, boolean) does not exist.”

Or

“The function blobs(int, int, int, boolean, int) does not exist.”

… which… have I installed the wrong version of OpenCV or something?

name=OpenCV for Processing
category=Video & Vision
... snip...
version=17
prettyVersion=0.5.4

Because, for instance, in a page which looks like OpenCV reference documentation, the example calls opencv.blobs so clearly this is expected to be provided somewhere.

Anyway blobDetection’s example sketch works out of the box, so it looks like this might be my best option for now.

hjh

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