Android系统OTG_usb链接摄像头的驱动和使用

原文地址：点击查看

这段时间做一个Android项目，需要在一台Android 4.4.4系统设备上链接usb摄像头，用作人脸识别，
于是作为Android项目组“骨干”（哈哈臭屁一下^-^）的我开始了usb摄像头攻坚战，爬帖子，找博客，
最后眼睛瞅准了一篇博客（感谢）
http://blog.youkuaiyun.com/sukhoi27smk/article/details/18269097

在他的帮助下我找到了
https://bitbucket.org/neuralassembly/simplewebcam/src

然后下载源码开始了我的usb摄像头驱动之旅

我整理的库文件下载点击查看

首先是在Linux Ubuntu系统下面配置环境，AS，NDK，如果想写C代码方便可以安装QT（个人推荐，其他都行，比如gedit就很好使）
软件安装，环境配置，这些自当不必多说。。。网上有N多种方式可以搞定

接下来就开始代码改造

找到jni文件夹下的ImageProc.c文件修改其中的jni接口方法名，使之指向CameraPreview.java

我修改后如下所示，找到其他的jni方法用同样方式修改方法名（不要忘了同步.h文件中的方法名哦。。。）：

void Java_com_mojsoft_usbcamera_view_CameraPreview_pixeltobmp( JNIEnv* env,jobject thiz,jobject bitmap)

Ctrl+Alt+T打开终端，cd到你的jni目录下，运行ndk-build,编译成功

cd .. 回到jni目录外面，运行ls就可以看到libs,obj两个目录，将libs中的libImageProc.so文件拷贝到你项目中的jniLibs目录下（AS）

接下来是java调用 [注意：java包名和C文件方法格式一致]

将CameraPreview文件放到布局中，编译运行。。。

接下来就是盯着屏幕。。。

满满的惊喜，问题就这么解决了，哈哈

下面是主要的CameraSurfaView类：

class CameraPreview extends SurfaceView implements SurfaceHolder.Callback, Runnable {

    private static final boolean DEBUG = true;
    private static final String TAG = "WebCam";
    protected Context context;
    private SurfaceHolder holder;
    Thread mainLoop = null;
    private Bitmap bmp = null;
    private byte[] byteArrary;

    private boolean cameraExists = false;
    private boolean shouldStop = false;

    // /dev/videox (x=cameraId+cameraBase) is used.
    // In some omap devices, system uses /dev/video[0-3],
    // so users must use /dev/video[4-].
    // In such a case, try cameraId=0 and cameraBase=4
    private int cameraId = 0;
    private int cameraBase = 0;

    // This definition also exists in ImageProc.h.
    // Webcam must support the resolution 640x480 with YUYV format.
    static final int IMG_WIDTH = 640;
    static final int IMG_HEIGHT = 480;

    // The following variables are used to draw camera images.
    private int winWidth = 0;
    private int winHeight = 0;
    private Rect rect;
    private int dw, dh;
    private float rate;
    private boolean isFramAready = false;
    private AlreadyRGBListener listener;

    // JNI functions
    public native int prepareCamera(int videoid);

    public native int prepareCameraWithBase(int videoid, int camerabase);

    public native void processCamera();

    public native void stopCamera();

    public native void pixeltobmp(Bitmap bitmap);

    public native byte[] getRgb();

    static {
    System.loadLibrary("ImageProc");
    }

    public CameraPreview(Context context) {
    super(context);
    this.context = context;
    if (DEBUG) Log.d(TAG, "CameraPreview constructed");
    setFocusable(true);

    holder = getHolder();
    holder.addCallback(this);
    holder.setType(SurfaceHolder.SURFACE_TYPE_NORMAL);
    }

    public CameraPreview(Context context, AttributeSet attrs) {
    super(context, attrs);
    this.context = context;
    if (DEBUG) Log.d(TAG, "CameraPreview constructed");
    setFocusable(true);

    holder = getHolder();
    holder.addCallback(this);
    holder.setType(SurfaceHolder.SURFACE_TYPE_NORMAL);
    }

    @Override
    public void run() {
    while (true && cameraExists) {
        //obtaining display area to draw a large image
        if (winWidth == 0) {
            winWidth = this.getWidth();
            winHeight = this.getHeight();

            if (winWidth * 3 / 4 <= winHeight) {
                dw = 0;
                dh = (winHeight - winWidth * 3 / 4) / 2;
                rate = ((float) winWidth) / IMG_WIDTH;
                rect = new Rect(dw, dh, dw + winWidth - 1, dh + winWidth * 3 / 4 - 1);
            } else {
                dw = (winWidth - winHeight * 4 / 3) / 2;
                dh = 0;
                rate = ((float) winHeight) / IMG_HEIGHT;
                rect = new Rect(dw, dh, dw + winHeight * 4 / 3 - 1, dh + winHeight - 1);
            }
        }

        // obtaining a camera image (pixel data are stored in an array in JNI).
        processCamera();
        // camera image to bmp
        pixeltobmp(bmp);

        byte[] arr = getRgb();

        isFramAready = true;

        Canvas canvas = getHolder().lockCanvas();
        if (canvas != null) {
            // draw camera bmp on canvas
            canvas.drawBitmap(bmp, null, rect, null);

            getHolder().unlockCanvasAndPost(canvas);
        }

        listener.alreadyRGB(arr);

        if (shouldStop) {
            shouldStop = false;
            break;
        }

    }
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
    if (DEBUG) Log.d(TAG, "surfaceCreated");
    if (bmp == null) {
        bmp = Bitmap.createBitmap(IMG_WIDTH, IMG_HEIGHT, Bitmap.Config.ARGB_8888);
    }
    if (byteArrary == null) {
        byteArrary = new byte[IMG_WIDTH * IMG_HEIGHT];
    }
    // /dev/videox (x=cameraId + cameraBase) is used
    //下面一句是原代码，我尝试失败，于是我将其修改为 int ret = prepareCamera(0);后成功调用
    // int ret = prepareCameraWithBase(cameraId, cameraBase);
    int ret = prepareCamera(0);
    if (ret != -1) cameraExists = true;

    mainLoop = new Thread(this);
    mainLoop.start();
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    if (DEBUG) Log.d(TAG, "surfaceChanged");
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
    if (DEBUG) Log.d(TAG, "surfaceDestroyed");
    if (cameraExists) {
        shouldStop = true;
        while (shouldStop) {
            try {
                Thread.sleep(50); // wait for thread stopping
            } catch (Exception e) {
            }
        }
    }
    stopCamera();
    }
    public void setGetBitmapListener(AlreadyRGBListener listener){
        this.listener = listener;
        }
}