swt-cctv/src/main/java/io/swtc/proccessing/WebcamCaptureLoop.java

package io.swtc.proccessing;

import com.github.sarxos.webcam.Webcam;
import com.github.sarxos.webcam.WebcamException;
import com.github.sarxos.webcam.WebcamResolution;

import java.awt.Dimension;
import java.awt.image.BufferedImage;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.LockSupport;
import java.util.function.Consumer;
import javax.swing.*;

import io.swtc.proccessing.ui.ShowError;

public class WebcamCaptureLoop {
    private final Webcam webcam;
    private final Consumer<BufferedImage> onFrameCaptured;
    private volatile boolean running = false;
    private final AtomicBoolean cleanedUp = new AtomicBoolean(false);
    private final int targetframes = 20;

    public WebcamCaptureLoop(Webcam webcam, Consumer<BufferedImage> onFrameCaptured) {
        this.webcam = webcam;
        this.onFrameCaptured = onFrameCaptured;

        Dimension vga = WebcamResolution.VGA.getSize();
        if (isSizeSupported(webcam, vga)) { // we dont do stupid shit anymore! cause we are smarter than before...
            webcam.setViewSize(vga);
        } else {
            Dimension[] dimensions = webcam.getViewSizes();
            webcam.setViewSize(dimensions[dimensions.length - 1]);
        }
    }

    private boolean isSizeSupported(Webcam webcam, Dimension vga) {
        for (Dimension d: webcam.getViewSizes()) {
            if (
                    d.width == vga.width && d.height == vga.height
            ) return true; // this should return 640x480 :)
        }
        return false;
    }

    public void start() {
        if (running) return;
        running = true;

        Thread captureThread = new Thread(() -> {
            try {
                if (!webcam.isOpen()) webcam.open(); // open if not

                long frameDurationLimitns = 1_000_000_000L / targetframes; // we use NanoSeconds cause its more accurate

                while (running) {
                    long startTime = System.nanoTime();

                    BufferedImage img = webcam.getImage();
                    if (img != null)
                        // there is no need for a invoke later swing wise!
                        onFrameCaptured.accept(img);

                    long timespent = System.nanoTime() - startTime;
                    long sleeptime = frameDurationLimitns - timespent;

                    if (sleeptime > 0) {
                        LockSupport.parkNanos(sleeptime);
                    } else {
                        // do a yield to prevent ui freezes
                        Thread.yield();
                    }
                }
            } catch (Exception e) {
                ShowError.warning(
                        null,
                        "Exception" + e,
                        "Exception"
                );
            } finally {
                cleanup();
            }
        }, "cam_cap_thread");
        captureThread.start();
    }

    /**
     * Safely release webcam
     */
    private synchronized void cleanup() {
        if (!cleanedUp.compareAndSet(false, true)) {
            return;
        }

        boolean success = false;

        try {
            if (webcam.isOpen())
                webcam.close();

            success = true;

        } catch (WebcamException exception) {
            SwingUtilities.invokeLater(() ->
            JOptionPane.showMessageDialog(
                    null,
                    "Cleanup failed \nWebCamException@"+exception.getMessage(),
                    "WebCamException",
                    JOptionPane.WARNING_MESSAGE // changed to warning, its better tbh
            ));
        } finally {
            if (!success)
                cleanedUp.set(false);
        }
    }

    /**
     * Arguments: null (or just none)
     * What does this method do? : Sets CameraThreads running flag to false and calls cleanup();
     */
    public void stop() {
        running = false;
    }
}