Hi all – I’ve been playing around with the BackgroundSubtraction example by Golan Levin in the Processing Video examples and have gotten comfortable with manipulating most aspects of the code in relationship to the image displayed, but there is a more technical part that I’m hoping someone can provide insight on. Currently, when a key is pressed, the image at time of pressing is stored and displayed; however, when you press a key again, that previous image is erased and then the new current image is stored and displayed. I’m wondering if it’s possible to keep storing and displaying every time the key is pressed, eg. if I press a key ten times, then there should be ten images stored and displayed… is this possible? And, then is it possible to press a key to erase all stored images?
G. Levin’s code:
/**
* Background Subtraction
* by Golan Levin.
*
* Detect the presence of people and objects in the frame using a simple
* background-subtraction technique. To initialize the background, press a key.
*/
import processing.video.*;
int numPixels;
int[] backgroundPixels;
Capture video;
void setup() {
fullScreen();
// This the default video input, see the GettingStartedCapture
// example if it creates an error
//video = new Capture(this, 160, 120);
video = new Capture(this, width, height);
// Start capturing the images from the camera
video.start();
numPixels = video.width * video.height;
// Create array to store the background image
backgroundPixels = new int[numPixels];
// Make the pixels[] array available for direct manipulation
loadPixels();
}
void draw() {
if (video.available()) {
video.read(); // Read a new video frame
video.loadPixels(); // Make the pixels of video available
// Difference between the current frame and the stored background
int presenceSum = 0;
for (int i = 0; i < numPixels; i++) { // For each pixel in the video frame...
// Fetch the current color in that location, and also the color
// of the background in that spot
color currColor = video.pixels[i];
color bkgdColor = backgroundPixels[i];
// Extract the red, green, and blue components of the current pixel's color
int currR = (currColor >> 16) & 0xFF;
int currG = (currColor >> 8) & 0xFF;
int currB = currColor & 0xFF;
// Extract the red, green, and blue components of the background pixel's color
int bkgdR = (bkgdColor >> 16) & 0xFF;
int bkgdG = (bkgdColor >> 8) & 0xFF;
int bkgdB = bkgdColor & 0xFF;
// Compute the difference of the red, green, and blue values
int diffR = abs(currR - bkgdR);
int diffG = abs(currG - bkgdG);
int diffB = abs(currB - bkgdB);
// Add these differences to the running tally
presenceSum += diffR + diffG + diffB;
// Render the difference image to the screen
//pixels[i] = color(diffR, diffG, diffB);
// The following line does the same thing much faster, but is more technical
pixels[i] = 0xFF000000 | (diffR << 16) | (diffG << 8) | diffB;
}
updatePixels(); // Notify that the pixels[] array has changed
println(presenceSum); // Print out the total amount of movement
}
}
// When a key is pressed, capture the background image into the backgroundPixels
// buffer, by copying each of the current frame's pixels into it.
void keyPressed() {
video.loadPixels();
arrayCopy(video.pixels, backgroundPixels);
}