Ref : https://developer.android.com/guide/topics/media/camera.html#custom-camera

add preview data
Ref : https://nidesai.wordpress.com/2013/09/22/android-camera-capturing-raw-video-frames/

draw text on camera preview
Ref : http://seshadripera.blogspot.tw/2013/04/how-to-draw-overlay-on-surfaceview-used.html

Detecting camera hardware

If your application does not specifically require a camera using a manifest declaration, you should check to see if a camera is available at runtime. To perform this check, use the PackageManager.hasSystemFeature() method, as shown in the example code below:

/** Check if this device has a camera */
private boolean checkCameraHardware(Context context) {
    if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){
        // this device has a camera
        return true;
    } else {
        // no camera on this device
        return false;
    }
}

Android devices can have multiple cameras, for example a back-facing camera for photography and a front-facing camera for video calls. Android 2.3 (API Level 9) and later allows you to check the number of cameras available on a device using the Camera.getNumberOfCameras() method.

Accessing cameras

If you have determined that the device on which your application is running has a camera, you must request to access it by getting an instance of Camera (unless you are using an intent to access the camera).

To access the primary camera, use the Camera.open() method and be sure to catch any exceptions, as shown in the code below:

/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
    Camera c = null;
    try {
        c = Camera.open(); // attempt to get a Camera instance
    }
    catch (Exception e){
        // Camera is not available (in use or does not exist)
    }
    return c; // returns null if camera is unavailable
}

Caution: Always check for exceptions when using Camera.open(). Failing to check for exceptions if the camera is in use or does not exist will cause your application to be shut down by the system.

On devices running Android 2.3 (API Level 9) or higher, you can access specific cameras using Camera.open(int). The example code above will access the first, back-facing camera on a device with more than one camera.

Checking camera features

Once you obtain access to a camera, you can get further information about its capabilities using the Camera.getParameters() method and checking the returned Camera.Parameters object for supported capabilities. When using API Level 9 or higher, use the Camera.getCameraInfo() to determine if a camera is on the front or back of the device, and the orientation of the image.

Creating a preview class

For users to effectively take pictures or video, they must be able to see what the device camera sees. A camera preview class is a SurfaceView that can display the live image data coming from a camera, so users can frame and capture a picture or video.

The following example code demonstrates how to create a basic camera preview class that can be included in a View layout. This class implements SurfaceHolder.Callback in order to capture the callback events for creating and destroying the view, which are needed for assigning the camera preview input.

  private SurfaceHolder mHolder;
    private Camera mCamera;

    public CameraPreview(Context context, Camera camera) {
        super(context);
        mCamera = camera;

        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        // deprecated setting, but required on Android versions prior to 3.0
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, now tell the camera where to draw the preview.
        try {
            mCamera.setPreviewDisplay(holder);
            mCamera.startPreview();
        } catch (IOException e) {
            Log.d(TAG, "Error setting camera preview: " + e.getMessage());
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // empty. Take care of releasing the Camera preview in your activity.
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // If your preview can change or rotate, take care of those events here.
        // Make sure to stop the preview before resizing or reformatting it.

        if (mHolder.getSurface() == null){
          // preview surface does not exist
          return;
        }

        // stop preview before making changes
        try {
            mCamera.stopPreview();
        } catch (Exception e){
          // ignore: tried to stop a non-existent preview
        }

        // set preview size and make any resize, rotate or
        // reformatting changes here

        // start preview with new settings
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();

        } catch (Exception e){
            Log.d(TAG, "Error starting camera preview: " + e.getMessage());
        }
    }

If you want to set a specific size for your camera preview, set this in the surfaceChanged() method as

noted in the comments above. When setting preview size, you must use values

from getSupportedPreviewSizes(). Do not set arbitrary values in the setPreviewSize() method.

Placing preview in a layout

A camera preview class, such as the example shown in the previous section, must be placed in the

layout of an activity along with other user interface controls for taking a picture or video. This section

shows you how to build a basic layout and activity for the preview.

The following layout code provides a very basic view that can be used to display a camera preview. In

this example, the FrameLayout element is meant to be the container for the camera preview class. This

layout type is used so that additional picture information or controls can be overlayed on the live

camera preview images.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
  <FrameLayout
    android:id="@+id/camera_preview"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_weight="1"
    />

  <Button
    android:id="@+id/button_capture"
    android:text="Capture"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    />
</LinearLayout>

On most devices, the default orientation of the camera preview is landscape. This example layout

specifies a horizontal (landscape) layout and the code below fixes the orientation of the application to

landscape. For simplicity in rendering a camera preview, you should change your application's preview

activity orientation to landscape by adding the following to your manifest.

<activity android:name=".CameraActivity"
          android:label="@string/app_name"

          android:screenOrientation="landscape">
          <!-- configure this activity to use landscape orientation -->

          <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>

Note: A camera preview does not have to be in landscape mode. Starting in Android 2.2 (API Level 8), you can use the setDisplayOrientation()method to set the rotation of the preview image. In order to change preview orientation as the user re-orients the phone, within the surfaceChanged() method of your preview class, first stop the preview with Camera.stopPreview() change the orientation and then start the preview again with Camera.startPreview().

In the activity for your camera view, add your preview class to the FrameLayout element shown in the

example above. Your camera activity must also ensure that it releases the camera when it is paused or

shut down. The following example shows how to modify a camera activity to attach the preview class

shown in Creating a preview class.

public class CameraActivity extends Activity {

    private Camera mCamera;
    private CameraPreview mPreview;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        // Create an instance of Camera
        mCamera = getCameraInstance();

        // Create our Preview view and set it as the content of our activity.
        mPreview = new CameraPreview(this, mCamera);
        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);
        preview.addView(mPreview);
    }
}

ote: The getCameraInstance() method in the example above refers to the example method shown in Accessing cameras.

Capturing pictures

Once you have built a preview class and a view layout in which to display it, you are ready to start

capturing images with your application. In your application code, you must set up listeners for your user

interface controls to respond to a user action by taking a picture.

In order to retrieve a picture, use the Camera.takePicture() method. This method takes three

parameters which receive data from the camera. In order to receive data in a JPEG format, you must

implement an Camera.PictureCallback interface to receive the image data and write it to a file. The

following code shows a basic implementation of the Camera.PictureCallback interface to save an

image received from the camera.

private PictureCallback mPicture = new PictureCallback() {

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {

        File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE);
        if (pictureFile == null){
            Log.d(TAG, "Error creating media file, check storage permissions: " +
                e.getMessage());
            return;
        }

        try {
            FileOutputStream fos = new FileOutputStream(pictureFile);
            fos.write(data);
            fos.close();
        } catch (FileNotFoundException e) {
            Log.d(TAG, "File not found: " + e.getMessage());
        } catch (IOException e) {
            Log.d(TAG, "Error accessing file: " + e.getMessage());
        }
    }
};

Ref : http://blog.csdn.net/bless2015/article/details/52075440

新建项目并装载OpenCV的so库函数

首先，很重要，先导入so库。

[java] view plaincopy
 print?
@Override  
public void onResume() {  
    super.onResume();  
    if (!OpenCVLoader.initDebug()) {  
        Log.d(TAG,  
                "Internal OpenCV library not found. Using OpenCV Manager for initialization");  
        OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_3_1_0, this,  
                mLoaderCallback);  
    } else {  
        Log.d(TAG, "OpenCV library found inside package. Using it!");  
        mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);  
    }  
}  

因为我用的3.1版本，所以用的这句话OpenCVLoader.OPENCV_VERSION_3_1_0，不同版本直接改后面的_3_1_0就好了（应该是这样，点进代码里简单看了看）。

单独写上边这行代码是报错的，我照着samples里这个项目的代码写的：

Ref : http://stackoverflow.com/questions/36204781/error-package-android-hardware-camera2-does-not-exist-opencv

Here's the build.gradle file of the OpenCV (3.0) module:

apply plugin: 'com.android.library'

android {
    compileSdkVersion 17
    buildToolsVersion "23.0.2"

defaultConfig {
    minSdkVersion 8
    targetSdkVersion 21
}

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
    }
}

Change compileSdkVersion 17 to minimum 21 (recommended 24). Because android.hardware.camera2 was added in API 21.

<?xml version="1.0" encoding="utf-8"?>
	<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:app="http://schemas.android.com/apk/res-auto"
	android:layout_width="match_parent"
	android:layout_height="match_parent">

	<!-- Content Container -->

	<android.support.design.widget.BottomNavigationView
	android:id="@+id/bottom_navigation"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:layout_alignParentBottom="true"
	app:itemBackground="@color/colorPrimary"
	app:itemIconTint="@color/white"
	app:itemTextColor="@color/white"
	app:menu="@menu/bottom_navigation_main" />

	</RelativeLayout>

android 的研究筆記

2017年6月2日星期五

2017年2月27日星期一

update apk

2017年2月25日星期六

ecpay app 串接

2017年2月22日星期三

grabcut on android sample

2017年2月14日星期二

Hosting a Website on linode

fast http get and post

2017年2月13日星期一

Implementing Bottom Navigation View in your app

svg to android xml website

dp 和 px 的轉換, sp 和 px的轉換

2016年11月27日星期日

2016年11月8日星期二

camera exposure time

2016年11月7日星期一

camera example

2016年11月1日星期二

video preview sample

Detecting camera hardware

Accessing cameras

Checking camera features

Creating a preview class

Placing preview in a layout

Capturing pictures

install opencv 310

新建项目并装载OpenCV的so库函数

2017年6月2日 星期五

2017年2月27日 星期一

2017年2月25日 星期六

2017年2月22日 星期三

2017年2月14日 星期二

2017年2月13日 星期一

2016年11月27日 星期日

2016年11月8日 星期二

2016年11月7日 星期一

2016年11月1日 星期二

Detecting camera hardware

Accessing cameras

Checking camera features

Creating a preview class

Placing preview in a layout

Capturing pictures

新建项目并装载OpenCV的so库函数

2017年6月2日星期五

2017年2月27日星期一

2017年2月25日星期六

2017年2月22日星期三

2017年2月14日星期二

2017年2月13日星期一

2016年11月27日星期日

2016年11月8日星期二

2016年11月7日星期一

2016年11月1日星期二