com.github.sarxos.webcam.WebcamMotionDetectorDefaultAlgorithm Maven / Gradle / Ivy

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This library allows you to use your PC webcam, IP or network cameras directly from Java. It's compatible with most operating systems (Windows, Linux, MacOS).
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package com.github.sarxos.webcam;

import com.github.sarxos.webcam.util.jh.JHBlurFilter;
import com.github.sarxos.webcam.util.jh.JHGrayFilter;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.ArrayList;

/**
 * Default motion detector algorithm.
 */
public class WebcamMotionDetectorDefaultAlgorithm implements WebcamMotionDetectorAlgorithm {

	/**
	 * Default pixel difference intensity threshold (set to 25).
	 */
	public static final int DEFAULT_PIXEL_THREASHOLD = 25;

	/**
	 * Default percentage image area fraction threshold (set to 0.2%).
	 */
	public static final double DEFAULT_AREA_THREASHOLD = 0.2;
	
	/**
	 * Pixel intensity threshold (0 - 255).
	 */
	private volatile int pixelThreshold = DEFAULT_PIXEL_THREASHOLD;

	/**
	 * Pixel intensity threshold (0 - 100).
	 */
	private volatile double areaThreshold = DEFAULT_AREA_THREASHOLD;

	/**
	 * Motion strength (0 = no motion, 100 = full image covered by motion).
	 */
	private double area = 0;

	/**
	 * Center of motion gravity.
	 */
	private Point cog = null;
	
	/**
	 * Blur filter instance.
	 */
	private final JHBlurFilter blur = new JHBlurFilter(6, 6, 1);

	/**
	 * Gray filter instance.
	 */
	private final JHGrayFilter gray = new JHGrayFilter();
	
	/**
	 * Creates default motion detector algorithm.
	 * 
	 * @param pixelThreshold intensity threshold (0 - 255)
	 * @param areaThreshold percentage threshold of image covered by motion
	 */
	public WebcamMotionDetectorDefaultAlgorithm(int pixelThreshold, double areaThreshold) {
		setPixelThreshold(pixelThreshold);
		setAreaThreshold(areaThreshold);
	}

	@Override
	public BufferedImage prepareImage(BufferedImage original) {
		BufferedImage modified = blur.filter(original, null);
		modified = gray.filter(modified, null);
		return modified;
	}

	@Override
	public boolean detect(BufferedImage previousModified, BufferedImage currentModified) {
        points.clear();
		int p = 0;

		int cogX = 0;
		int cogY = 0;

		int w = currentModified.getWidth();
		int h = currentModified.getHeight();

        int j = 0;
		if (previousModified != null) {
			for (int x = 0; x < w; x++) {
				for (int y = 0; y < h; y++) {

					int cpx = currentModified.getRGB(x, y);
					int ppx = previousModified.getRGB(x, y);
					int pid = combinePixels(cpx, ppx) & 0x000000ff;

					if (pid >= pixelThreshold) {
                        Point pp = new Point(x, y);
                        boolean keep = j < maxPoints;

                        if (keep) {
                            for (Point g : points) {
                                if (g.x != pp.x || g.y != pp.y) {
                                    if (pp.distance(g) <= range) {
                                        keep = false;
                                        break;
                                    }
                                }
                            }
                        }

                        if (keep) {
                            points.add(new Point(x, y));
                            j += 1;
                        }

                        cogX += x;
                        cogY += y;
                        p += 1;
                    }
				}
			}
		}

		area = p * 100d / (w * h);
		
		if (area >= areaThreshold) {
			cog = new Point(cogX / p, cogY / p);
			return true;
		} else {
			cog = new Point(w / 2, h / 2);
			return false;
		}
	}

	@Override
	public Point getCog() {
		return this.cog;
	}

	@Override
	public double getArea() {
		return this.area;
	}
	
	/**
	 * Set pixel intensity difference threshold above which pixel is classified
	 * as "moved". Minimum value is 0 and maximum is 255. Default value is 10.
	 * This value is equal for all RGB components difference.
	 *
	 * @param threshold the pixel intensity difference threshold
	 * @see #DEFAULT_PIXEL_THREASHOLD
	 */
	public void setPixelThreshold(int threshold) {
		if (threshold < 0) {
			throw new IllegalArgumentException("Pixel intensity threshold cannot be negative!");
		}
		if (threshold > 255) {
			throw new IllegalArgumentException("Pixel intensity threshold cannot be higher than 255!");
		}
		this.pixelThreshold = threshold;
	}

	/**
	 * Set percentage fraction of detected motion area threshold above which it
	 * is classified as "moved". Minimum value for this is 0 and maximum is 100,
	 * which corresponds to full image covered by spontaneous motion.
	 *
	 * @param threshold the percentage fraction of image area
	 * @see #DEFAULT_AREA_THREASHOLD
	 */
	public void setAreaThreshold(double threshold) {
		if (threshold < 0) {
			throw new IllegalArgumentException("Area fraction threshold cannot be negative!");
		}
		if (threshold > 100) {
			throw new IllegalArgumentException("Area fraction threshold cannot be higher than 100!");
		}
		this.areaThreshold = threshold;
	}
	
	private static int combinePixels(int rgb1, int rgb2) {

		// first ARGB

		int a1 = (rgb1 >> 24) & 0xff;
		int r1 = (rgb1 >> 16) & 0xff;
		int g1 = (rgb1 >> 8) & 0xff;
		int b1 = rgb1 & 0xff;

		// second ARGB

		int a2 = (rgb2 >> 24) & 0xff;
		int r2 = (rgb2 >> 16) & 0xff;
		int g2 = (rgb2 >> 8) & 0xff;
		int b2 = rgb2 & 0xff;

		r1 = clamp(Math.abs(r1 - r2));
		g1 = clamp(Math.abs(g1 - g2));
		b1 = clamp(Math.abs(b1 - b2));

		// in case if alpha is enabled (translucent image)

		if (a1 != 0xff) {
			a1 = a1 * 0xff / 255;
			int a3 = (255 - a1) * a2 / 255;
			r1 = clamp((r1 * a1 + r2 * a3) / 255);
			g1 = clamp((g1 * a1 + g2 * a3) / 255);
			b1 = clamp((b1 * a1 + b2 * a3) / 255);
			a1 = clamp(a1 + a3);
		}

		return (a1 << 24) | (r1 << 16) | (g1 << 8) | b1;
	}

	/**
	 * Clamp a value to the range 0..255
	 */
	private static int clamp(int c) {
		if (c < 0) {
			return 0;
		}
		if (c > 255) {
			return 255;
		}
		return c;
	}


    /**
     * ArrayList to store the points for a detected motion
     */
    ArrayList points = new ArrayList();

    /**
     * The default minimum range between each point where motion has been detected
     */
    public static final int DEFAULT_RANGE = 50;

    /**
     * The default for the max amount of points that can be detected at one time
     */
    public static final int DEFAULT_MAX_POINTS = 100;

    /**
     * The current minimum range between points
     */
    private int range = DEFAULT_RANGE;

    /**
     * The current max amount of points
     */
    private int maxPoints = DEFAULT_MAX_POINTS;

    /**
     * Set the minimum range between each point detected
     * @param i the range to set
     */
    public void setPointRange(int i){
        range = i;
    }

    /**
     * Get the current minimum range between each point
     * @return The current range
     */
    public int getPointRange(){
        return range;
    }


    /**
     * Set the max amount of points that can be detected at one time
     * @param i The amount of points that can be detected
     */
    public void setMaxPoints(int i){
        maxPoints = i;
    }


    /**
     * Get the current max amount of points that can be detected at one time
     * @return
     */
    public int getMaxPoints(){
        return maxPoints;
    }

    /**
     * Returns the currently stored points that have been detected
     * @return The current points
     */
    public ArrayList getPoints(){
        return points;
    }
}