Android圖片的合成

mainActivity如下:

package c.c;import android.app.Activity;import android.content.Intent;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.PorterDuffXfermode;import android.net.Uri;import android.os.Bundle;import android.provider.MediaStore;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.ImageView;/** * 需求描述: * 從相簿中選取兩張圖片合成一張圖片 *  * 小結: * 1 依據圖片的Uri載入圖片 * mBitmap1=BitmapFactory.decodeStream * (getContentResolver().openInputStream(photoFileUri)); * 為什麼使用getContentResolver呢？因為在相簿本身是一個內容提供者 * 2 注意構造方法: * Canvas canvas=new Canvas(bitmap); * 為什麼要傳入一個bitmap呢？ * 我們畫東西肯定是在畫布上畫. * 但是在這裡傳入一個bitmap * 即該bitmap是一個載體,相當於把bitmap作為了畫布. * 當然本質上是:把東西畫在了canvas裡的bitmap上 * 也可以這麼想: * 我們最後不是要用mImageView.setImageBitmap(參數是一個Bitmap)來顯示 * 一張圖片嗎？所以在構造Canvas的時候傳入了一個Bitmap.然後把兩張圖片 * 畫到了該Bitmap上.最後該Bitmap就是兩張照片的合成圖. * 所以當然要把兩張圖片畫到一個Bitmap上 */public class MainActivity extends Activity {private static int REQUESTCODE=0;private final static int PICK_FIRST_PHOTO=1;private final static int PICK_SECOND_PHOTO=2;private boolean isPickedFirstPhoto=false;private boolean isPickedSecondPhoto=false;    private Button mButton1;    private Button mButton2;    private Bitmap mBitmap1;    private Bitmap mBitmap2;    private ImageView mImageView;        @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        init();    }    private void init(){    mButton1=(Button) findViewById(R.id.button1);    mButton1.setOnClickListener(new ButtonOnClickListenerImpl());    mButton2=(Button) findViewById(R.id.button2);    mButton2.setOnClickListener(new ButtonOnClickListenerImpl());    mImageView=(ImageView) findViewById(R.id.imageView);    }    private class ButtonOnClickListenerImpl implements OnClickListener{public void onClick(View v) {if (v.getId()==R.id.button1) {REQUESTCODE=PICK_FIRST_PHOTO;} else {REQUESTCODE=PICK_SECOND_PHOTO;}Intent intent=new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);startActivityForResult(intent, REQUESTCODE);}        }    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {    super.onActivityResult(requestCode, resultCode, data);    if (resultCode==RESULT_OK) {    Uri photoFileUri=data.getData();if (requestCode==PICK_FIRST_PHOTO) {try {mBitmap1=BitmapFactory.decodeStream(getContentResolver().openInputStream(photoFileUri));isPickedFirstPhoto=true;} catch (Exception e) {e.printStackTrace();}}if (requestCode==PICK_SECOND_PHOTO) {try {mBitmap2=BitmapFactory.decodeStream(getContentResolver().openInputStream(photoFileUri));isPickedSecondPhoto=true;} catch (Exception e) {e.printStackTrace();}}if (isPickedFirstPhoto&&isPickedSecondPhoto) {Bitmap bitmap=Bitmap.createBitmap(mBitmap1.getWidth(), mBitmap1.getHeight(), mBitmap1.getConfig());Canvas canvas=new Canvas(bitmap);Paint paint=new Paint();canvas.drawBitmap(mBitmap1, 0, 0, paint);paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.MULTIPLY));canvas.drawBitmap(mBitmap2, 0, 0,paint);mImageView.setImageBitmap(bitmap);}}    }}

main.xml如下:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent" >    <Button        android:id="@+id/button1"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:layout_centerHorizontal="true"        android:text="選擇第一張圖片"         />    <Button        android:id="@+id/button2"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:layout_centerHorizontal="true"        android:layout_below="@id/button1"        android:text="選擇第二張圖片"     />    <ImageView       android:id="@+id/imageView"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:layout_centerInParent="true"        android:layout_below="@id/button2"     /></RelativeLayout>