四十五、android camera

1.关于预览横竖差90度的问题
原因分析 

      经过查证和实验，可以证实：Android提供的SDK（android.hardware.Camera）里大概不能正常的使用竖屏（portrait layout）加载照相机，当用竖屏模式加载照相机时会产生以下情况：1. 照相机成像左倾90度（倾斜）；2. 照相机成像长宽比例不对（失比）。之所以是“大概”，原因是因为可能可以通过一些比较复杂的手段解决。如果以上成立，那为什么竖屏不能正常成像也就很显然了。为什么会产生这样的情况，请看下面的研究分析。
      照相机在一般情况下是必须用landscape layout（横屏）的，可以证明，先写一个照相机（只要能preview就行），如果Manifest的activity里不加入android:screenOrientation="landscape"，即默认了 android:screenOrientation="portrait"（竖屏），照相机preview时就会出现左倾90度的现象，并且失比。原因是这样的（我推测的），摄像头对照物的映射是Android底层固定了的，以landscape方式为正，并且产生大小为320*480的像，如果换成portrait方式了，摄像头还是产生320*480的像，然后分别对应的放入到一个480*320的屏内，显然会失比，然后根据竖、横屏的规则，就产生了左倾90度的情况（图例见左）。为了进一步证实我对失比原因的推测，我照相机内加载的SurfaceView调成了320*213，比例大概是(320:213)*1.5=(480:320)，所成像结果如愿的形成左倾但是没有失比的状况，这就证实了我的想法。

              

综上可以看出，左倾是因为摄像头映射产生的，而失比是由于像素比例映射产生的。
解决方案
暂无好的解决方案，只能强制横屏，记载代码中加入
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE); 
暂无好的解决方案，只能强制横屏，记载代码中加入
android:screenOrientation="landscape"
          

2.关于拍出来的照片不能正确成像，如绿屏，红绿相间，重叠等
原因分析

有的手机不支持parameter.setPictureSize(width,height)、parameters.setPreviewSize(width,height)方法，为了兼容性建议不设置这两个方法。

             

附：完整示例代码
main.xml布局文件

?

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical" >

    <LinearLayout

        xmlns:android="http://schemas.android.com/apk/res/android"

        android:layout_width="fill_parent"

        android:layout_height="fill_parent"

        android:orientation="vertical"

        android:layout_weight="2">

        <SurfaceView

            android:id="@+id/surfaceView"

            android:layout_width="fill_parent"

            android:layout_height="fill_parent" />

    </LinearLayout>

    <LinearLayout

        xmlns:android="http://schemas.android.com/apk/res/android"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:orientation="horizontal"

        android:layout_weight="1"

        android:background="@android:color/white"

        android:layout_gravity="center">

        <ImageButton android:layout_width="fill_parent"

            android:layout_height="80dip"

            android:id="@+id/btnTakePicture"

            android:layout_gravity="center"

            android:textSize="30dip"

            android:layout_weight="1"

            android:src="@drawable/btn_take_pic"/>

        <ImageButton android:layout_width="fill_parent"

            android:layout_height="80dip"

            android:id="@+id/btnAutoFocus"

            android:layout_gravity="center"

            android:textSize="30dip"

            android:layout_weight="1"

            android:src="@drawable/btn_auto_focus"/>

    </LinearLayout>

 

</LinearLayout>

                

二、MainActivity拍照核心代码

 

?

package cn.itcast.takepicture;

 

import java.io.File;

import java.io.FileOutputStream;

 

import android.app.Activity;

import android.content.pm.ActivityInfo;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.Matrix;

import android.graphics.PixelFormat;

import android.graphics.Bitmap.CompressFormat;

import android.hardware.Camera;

import android.hardware.Camera.PictureCallback;

import android.os.Bundle;

import android.os.Environment;

import android.view.SurfaceHolder;

import android.view.SurfaceView;

import android.view.View;

import android.view.Window;

import android.view.WindowManager;

import android.view.SurfaceHolder.Callback;

import android.widget.ImageButton;

 

public class MainActivity extends Activity {

    private ImageButton btnTakePicture = null;

    private ImageButton btnAutoFocus = null;

    private Camera camera = null;

 

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        // 设置窗口标题

        requestWindowFeature(Window.FEATURE_NO_TITLE);

        // 横屏

        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

        // 全屏显示

        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,

                WindowManager.LayoutParams.FLAG_FULLSCREEN);

        // 当此窗口为用户可见时，保持设备常开，并保持亮度不变。

        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        setContentView(R.layout.main);

 

        SurfaceView surfaceView = (SurfaceView) this

                .findViewById(R.id.surfaceView);

        surfaceView.getHolder()

                .setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

        surfaceView.getHolder().setFixedSize(320, 240); // 设置分辨率

        surfaceView.getHolder().addCallback(new SurfaceCallback());

        btnTakePicture = (ImageButton) findViewById(R.id.btnTakePicture);

        btnAutoFocus = (ImageButton) findViewById(R.id.btnAutoFocus);

        btnTakePicture.setOnClickListener(onClickListener);

        btnAutoFocus.setOnClickListener(onClickListener);

    }

 

    private final View.OnClickListener onClickListener = new View.OnClickListener() {

 

        @Override

        public void onClick(View v) {

            if (v == btnTakePicture) {

                if (camera != null)

                    camera.takePicture(null, null, new TakePictureCallback()); // 拍照

            } else if (v == btnAutoFocus) {

                if (camera != null)

                    camera.autoFocus(null); // 对焦

            }

        }

    };

 

    private final class SurfaceCallback implements Callback {

        private boolean preview; // 是否正在预览

 

        @Override

        public void surfaceChanged(SurfaceHolder holder, int format, int width,

                int height) {

 

        }

 

        @Override

        public void surfaceCreated(SurfaceHolder holder) {

            try {

                camera = Camera.open();

                Camera.Parameters parameters = camera.getParameters();

                parameters.setPreviewFrameRate(5); //每秒5帧

                parameters.setPictureFormat(PixelFormat.JPEG);//设置照片的输出格式

                parameters.set("jpeg-quality", 85);//照片质量

                camera.setParameters(parameters);

                camera.setPreviewDisplay(holder);

                camera.startPreview();

                preview = true;

            } catch (Exception e) {

                e.printStackTrace();

            }

        }

 

        @Override

        public void surfaceDestroyed(SurfaceHolder holder) {

            if (camera != null) {

                if (preview) {

                    camera.stopPreview();

                    preview = false;

                }

                camera.release();

                camera = null; // 记得释放

            }

        }

    }

 

    private final class TakePictureCallback implements PictureCallback {

 

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

            Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);

            Matrix matrix=new Matrix();

            //设置缩放

            matrix.postScale(0.5f, 0.5f);

            bitmap=Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);

            File file = new File(Environment.getExternalStorageDirectory(),

                    System.currentTimeMillis() + ".jpg");

            try {

                FileOutputStream outStream = new FileOutputStream(file);

                bitmap.compress(CompressFormat.JPEG, 100, outStream);

                outStream.close();

                camera.startPreview();

            } catch (Exception e) {

                e.printStackTrace();

            }

        }

 

    }

 

}

             

清单文件

?

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="cn.itcast.takepicture"

    android:versionCode="1"

    android:versionName="1.0" >

 

    <application

        android:icon="@drawable/icon"

        android:label="@string/app_name" >

        <activity

            android:label="@string/app_name"

            android:name=".MainActivity" >

            <intent-filter >

                <action android:name="android.intent.action.MAIN" />

 

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

    </application>

 

    <uses-sdk android:minSdkVersion="7" />

 

    <uses-permission android:name="android.permission.CAMERA" />

    <!-- 在SDCard中创建与删除文件权限 -->

    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />

    <!-- 往SDCard写入数据权限 -->

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

 

</manifest>