Android:使用Canvas合并Bitmap

• 关键点

canvas.drawBitmap(bitmap, srcRect, dstRect, null);

将bitmap的srcRect区域绘制到canvas的dstRect区域

• Demo

main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/rl_root"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/background_dark"
    android:orientation="horizontal" >
    <ImageView
        android:id="@+id/iv_bmp1"
        android:layout_width="80dp"
        android:layout_height="100dp"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="20dp"
        android:layout_marginStart="20dp"
        android:layout_marginTop="20dp"
        android:contentDescription="@null"
        android:src="@drawable/baby" />
    <ImageView
        android:id="@+id/iv_bmp2"
        android:layout_width="80dp"
        android:layout_height="100dp"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_marginEnd="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="20dp"
        android:contentDescription="@null"
        android:src="@drawable/baby2" />
    <Button
        android:id="@+id/btn_merge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/iv_bmp1"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="20dp"
        android:text="Merge" />
    <ImageView
        android:id="@+id/iv_bmp_merge"
        android:layout_width="160dp"
        android:layout_height="100dp"
        android:layout_below="@id/btn_merge"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="20dp"
        android:contentDescription="@null" />
</RelativeLayout>

目的就是将ivBmp1和ivBmp2上的图片，合并之后，显示在iv_bmp_merger上

• MainActivity.java

package net.mobctrl.mergebitmap;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Handler.Callback;
import android.os.Message;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

/**
 * 
 * @author Zheng Haibo
 * @web http://www.mobctrl.net
 *
 */
public class MainActivity extends Activity {

    private ImageView ivBmp1;
    private ImageView ivBmp2;
    private ImageView ivBmpMerge;
    private Button mergeBtn;

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

    private void initUi() {
        ivBmp1 = (ImageView) findViewById(R.id.iv_bmp1);
        ivBmp2 = (ImageView) findViewById(R.id.iv_bmp2);
        ivBmpMerge = (ImageView) findViewById(R.id.iv_bmp_merge);
        mergeBtn = (Button) findViewById(R.id.btn_merge);
        mergeBtn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                showMergeBitmap();
            }
        });

    }

    private Handler handler = new Handler(new Callback() {

        @Override
        public boolean handleMessage(Message msg) {
            Bitmap bitmap = (Bitmap) msg.obj;
            ivBmpMerge.setImageBitmap(bitmap);
            return false;
        }
    });

    /**
     * 显示合并的图
     */
    protected void showMergeBitmap() {
        new Thread(new Runnable() {

            @Override
            public void run() {
                Bitmap bitmap = mergeBitmap();
                Message messge = handler.obtainMessage();
                messge.obj = bitmap;
                handler.sendMessage(messge);
            }
        }).start();
    }

    /*
     * 使用Canvas合并Bitmap
     */
    private Bitmap mergeBitmap() {
        // 获取ImageView上得Bitmap图片
        Bitmap bmp1 = ((BitmapDrawable) ivBmp1.getDrawable()).getBitmap();
        Bitmap bmp2 = ((BitmapDrawable) ivBmp2.getDrawable()).getBitmap();

        // 创建空得背景bitmap
        // 生成画布图像
        Bitmap resultBitmap = Bitmap.createBitmap(ivBmpMerge.getWidth(),
                ivBmpMerge.getHeight(), Bitmap.Config.RGB_565);
        Canvas canvas = new Canvas(resultBitmap);// 使用空白图片生成canvas

        // 将bmp1绘制在画布上
        Rect srcRect = new Rect(0, 0, bmp1.getWidth(), bmp1.getHeight());// 截取bmp1中的矩形区域
        Rect dstRect = new Rect(0, 0, ivBmpMerge.getWidth() / 2,
                ivBmpMerge.getHeight());// bmp1在目标画布中的位置
        canvas.drawBitmap(bmp1, srcRect, dstRect, null);

        // 将bmp2绘制在画布上
        srcRect = new Rect(0, 0, bmp2.getWidth(), bmp2.getHeight());// 截取bmp1中的矩形区域
        dstRect = new Rect(ivBmpMerge.getWidth() / 2, 0, ivBmpMerge.getWidth(),
                ivBmpMerge.getHeight());// bmp2在目标画布中的位置
        canvas.drawBitmap(bmp2, srcRect, dstRect, null);
        // 将bmp1,bmp2合并显示
        return resultBitmap;
    }

}

• 运行效果
  
  点击merge之后