• 使用树莓派制作简易监控模块


        几年前买的Raspberry P 1 (CPU: 700MHz ARM,  Memory: 512MB) 已积灰很久, 偶然发现尝试做使用它的拍照功能做监控,如下图:

    1、系统安装与配置

      首先安装 raspbian-jessie-lite (官方下载),在windows下使用win32diskimager写入SD卡比较容易。

      其次插入SD卡,接通电源启动系统。对于没有显示器(也没有外接的键盘)的情况下,只能选择网络方式访问。遇到了一些问题

      (1)  虽然可以通过家庭路由器得到DHCP分配的IP(或者根据ARP,甚至使用nmap扫描)得到这个树莓派的IP,但是前提要求网络环境比较高。

      (2)  从2016.11月以后,Raspbian系统默认关闭SSH(估计是考虑安全性),也就是系统启动后SSH服务根本没启动。

    这种情况下只能通过修改系统里面的IP等相关参数使得启动后能得到固定的IP。对于在windows下读写Linux分区始终是个不方便的事。

    查找了多方面资料,只有Ext2Fsd能满足要求,但是按照后插入SD卡却变成了下图这样:

    结果Linux分区无法成为一个被Ext2Fsd识别的卷,所以这个办法就到这里终止了。也尝试过将整个系统刻入SD卡(使用EXT3),但是系统无法启动。

    最后,只能通过Linux系统来读写这个Linux分区。在这里使用back track 5来制作一个U盘系统然后重启笔记本,尝试通过笔记本修改SD卡里面的系统参数。

    SD卡在BT5下挂载成功:

    然后修改 /etc/network/interfaces文件,配置一个固定IP,如下:

    现在IP确定了,但是还有SSH默认情况下是关闭的,所以需要开机启动,修改/etc/rc.local文件,加入SSH的启动命令,如下图:

    然后umount SD卡后插入树莓派启动,状态灯显示工作正常,如下图:

    然后使用笔记本尝试ping&ssh:

    C:>ping 192.168.0.125
    
    Pinging 192.168.0.125 with 32 bytes of data:
    Reply from 192.168.0.125: bytes=32 time=3ms TTL=64
    Reply from 192.168.0.125: bytes=32 time=4ms TTL=64
    Reply from 192.168.0.125: bytes=32 time=2ms TTL=64
    Reply from 192.168.0.125: bytes=32 time=3ms TTL=64
    
    Ping statistics for 192.168.0.125:
        Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
    Approximate round trip times in milli-seconds:
        Minimum = 2ms, Maximum = 4ms, Average = 3ms
    The programs included with the Debian GNU/Linux system are free software;
    the exact distribution terms for each program are described in the
    individual files in /usr/share/doc/*/copyright.
    
    Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
    permitted by applicable law.
    Last login: Thu Aug 10 20:37:32 2017 from 192.168.0.210
    
    
    pi@x:~$ 
    pi@x:~$ 

    至此,系统配置成功,下面可以通过raspi-config命令启用SSH功能了,然后把rc.local中的启动命令删除,另外更改密码。

    2. 监控拍摄对比

    通过raspi-config工具启用Camera功能并把摄像模块插入,然后就可以使用raspistill工具进行拍照了。

    再这里使用Java开发定时拍照任务并做图像对比,由于Camera不能通过Java直接调用,在这里就使用了jrpicam (https://github.com/Hopding/JRPiCam) 开源组件,

    通过调用raspistill进行拍照然后得到图像,整个工程的建立如下图,我将从github得到的源码一起合并到工程里面,工程就叫做smallcat吧(像一只猫一样盯着):

    2个类,一个Camera类是拍照获得图像的:

    public class Camera {
        
        private RPiCamera piCamera = null;
        private String defaultSaveDir = "/home/pi/diff-photo";
        
        public Camera() {
            try {
                piCamera = new RPiCamera(defaultSaveDir);
            } catch (FailedToRunRaspistillException e) {
                e.printStackTrace();
            }
        }
        
        public BufferedImage takeOnePhoto() throws Exception {
            piCamera.setAWB(AWB.AUTO)       // Change Automatic White Balance setting to automatic
                .setDRC(DRC.OFF)            // Turn off Dynamic Range Compression
                .setContrast(100)
                .setSharpness(100)
                .setQuality(100)
                .setTimeout(1)
                .setBrightness(75)
                .turnOnPreview()            // Turn on image preview
                .setEncoding(Encoding.PNG); // Change encoding of images to PNG
            
            BufferedImage buffImg = piCamera.takeBufferedStill(800, 600); // Take image and store in BufferedImage
            return buffImg;
        }
        
    }

    还有一个MyCat是主任务类,获取图像后对比,符合条件后保存图像:

    public class MyCat {
        
        private Camera camera = null;
        private double diffPercentThreshold = 4.0;
        
        private String diffPhotoSaveDir = "/home/pi/diff-photo/";
        
        public static void main(String[] args) {
            System.out.println("My-Cat starting...");
            MyCat cat = new MyCat();
            cat.wakeUpMyCat();
            System.out.println("My-Cat started!");
        }
        
        public void wakeUpMyCat() {
            camera = new Camera();
            Thread inspector = new Thread(new CatInspector());
            inspector.setName("Cat-Inspector");
            inspector.start();
        }
        
        class CatInspector implements Runnable {
            private BufferedImage previousPhoto = null;
            
            @Override
            public void run() {
                while (true) {
                    try {
                        TimeUnit.SECONDS.sleep(3);
                    } catch (InterruptedException e1) {
                        System.out.println("Cat Inspector Interrupted");
                        return;
                    }
                    
                    try {
                        BufferedImage currentPhoto = camera.takeOnePhoto();
                        if (previousPhoto != null) {
                            if (isDifferent(currentPhoto)) {
                                foundDiffPhoto(currentPhoto);
                            }
                        } else {
                            // Save the first photo
                            foundDiffPhoto(currentPhoto);
                        }
                        
                        previousPhoto = currentPhoto; // Set current photo as previous
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
            
            /**
             * Process different photo
             */
            private void foundDiffPhoto(BufferedImage photo) {
                String fileName = new SimpleDateFormat("yyyyMMddHHmmss").format(new Date());
                File saveFile = new File(diffPhotoSaveDir + fileName + ".png");
                try {
                    ImageIO.write(photo, "png", saveFile);
                    System.out.println("New image saved to: " + saveFile.getAbsolutePath());
                } catch (IOException e) {
                    System.out.println("Save image error: ");
                    e.printStackTrace();
                }
            }
            
            /**
             * Compare current photo with previous photo
             */
            private boolean isDifferent(BufferedImage currentPhoto) {
                int currentWidth = currentPhoto.getWidth();
                int currentHeight = currentPhoto.getHeight();
                
                int previousWidth = previousPhoto.getWidth();
                int previousHeight = previousPhoto.getHeight();
                
                if ((currentWidth != previousWidth) || (currentHeight != previousHeight)) {
                    System.err.println("Error: Images dimensions mismatch");
                    System.exit(1);
                }
                long diff = 0;
                // Find RGB difference
                for (int y = 0; y < currentHeight; y++) {
                    for (int x = 0; x < currentWidth; x++) {
                        int rgb1 = currentPhoto.getRGB(x, y);
                        int rgb2 = previousPhoto.getRGB(x, y);
                        
                        int r1 = (rgb1 >> 16) & 0xff;
                        int g1 = (rgb1 >> 8) & 0xff;
                        int b1 = (rgb1) & 0xff;
                        
                        int r2 = (rgb2 >> 16) & 0xff;
                        int g2 = (rgb2 >> 8) & 0xff;
                        int b2 = (rgb2) & 0xff;
                        
                        diff += Math.abs(r1 - r2);
                        diff += Math.abs(g1 - g2);
                        diff += Math.abs(b1 - b2);
                    }
                }
                double n = currentWidth * currentHeight * 3;
                double p = diff / n / 255.0;
                
                double diffPercent = (p * 100.0);
                System.out.println("Diff percent: " + diffPercent);
                return diffPercent > diffPercentThreshold;
            }
        }
        
    }

    图像的相似性匹配是一个复杂的论题,这里使用最简单的RGB值比对(复杂的算法这个小树莓很难承受),每次比对后睡眠3秒钟后面再执行任务。

    打包jar放到树莓派上面执行吧,但首先需要安装下JDK:

    # sudo apt-get update
    # sudo apt-get install oracle-java7-jdk

    3. 结果如何 ?

    (1)  得到记录的两张图片如下(相似比例调试到一个比较合适的值)。

     

    (2)  这个摄像头确实比较差,尝试调整参数效果也不理想,没有自动对焦等功能对于监控来说实际上用起来困难。

    (3)  简单的RGB循环对比,CPU一下子撑到80-90%,这个单核的700MHz CPU做这类工作确定有点困难,高负载的时候SSH经常卡顿。

    (4)  总之,实用性不强。

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  • 原文地址:https://www.cnblogs.com/mikevictor07/p/7343099.html
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