关于如何用纯OpenCV实现图片叠加的例子实在是太少，太多的是使用 C++,JNI实现的，如果要用C++的话，我们为啥不转行做C++

下面的例子基于 Android JavaCV 实现了在im_beauty 美女图片上  添加im_flower3 小花图片 并显示

需要在res/drawable目录下 放两个文件 im_beauty, im_flower3 注意im_flower3一定要比im_beauty图片尺寸要下小

package com.KyleOpencvImageAdd;

import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.LoaderCallbackInterface;
import org.opencv.android.OpenCVLoader;
import org.opencv.android.Utils;
import org.opencv.core.Mat;
import org.opencv.core.Rect;


import android.os.Bundle;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity extends Activity implements OnClickListener {

	private Mat mat1,mat2;
	private ImageView iv1,iv2;
	//用于显示两张图片叠加
	private ImageView iv3;
	private Button btn;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		//初始化图片显示
		iv1=(ImageView)findViewById(R.id.imageView1);
		 iv1.setImageResource(R.drawable.im_beauty);
		 
		iv2=(ImageView)findViewById(R.id.imageView2);
		 iv2.setImageResource(R.drawable.im_flower3);
		 
		iv3=(ImageView)findViewById(R.id.imageView3);
		
		btn=(Button)findViewById(R.id.button1);
		btn.setOnClickListener(this);
	}
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}
    private BaseLoaderCallback  mLoaderCallback = new BaseLoaderCallback(this) {

		@Override
        public void onManagerConnected(int status) {
            switch (status) {
                case LoaderCallbackInterface.SUCCESS:
                {
                    Log.i("", "OpenCV loaded successfully");

                 
                } break;
                default:
                {
                    super.onManagerConnected(status);
                } break;
            }
        }
    };

		@Override
		protected void onResume() {
			// TODO Auto-generated method stub
			super.onResume();
			//初始化函数库
			OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_2_4_3, this, mLoaderCallback);
		}

	@Override
	public void onClick(View arg0) {
		// 初始化数据
		mat1 = new Mat();
		mat2 = new Mat();
		Mat mat1Sub = new Mat();

		// 加载图片
		Bitmap bt1 = BitmapFactory.decodeResource(getResources(),
				R.drawable.im_beauty);
		Bitmap bt2 = BitmapFactory.decodeResource(getResources(),
				R.drawable.im_flower3);
		Bitmap bt3 = null;

		// 转换数据
		Utils.bitmapToMat(bt1, mat1);
		Utils.bitmapToMat(bt2, mat2);

		/** 方法一加权 高级方式 可实现水印效果*********/

		// mat1Sub=mat1.submat(0, mat2.rows(), 0, mat2.cols());
		// Core.addWeighted(mat1Sub, 1, mat2, 0.3, 0., mat1Sub);

		/** 方法二 求差 ********/

		// submat(y坐标, 图片2的高, x坐标，图片2的宽);
		// mat1Sub=mat1.submat(0, mat2.rows(), 0, mat2.cols());
		// mat2.copyTo(mat1Sub);

		/*** 方法三兴趣区域裁剪 **/
		// 定义感兴趣区域Rect(x坐标，y坐标,图片2的宽，图片2的高)
		Rect rec = new Rect(0, 0, mat2.cols(), mat2.rows());
		// submat(y坐标, 图片2的高, x坐标，图片2的宽);
		mat1Sub = mat1.submat(rec);
		mat2.copyTo(mat1Sub);
        //转化为android识别的图像数据注意bt3的宽高要和mat1一至
		bt3 = Bitmap.createBitmap(mat1.cols(), mat1.rows(), Config.RGB_565);
		Utils.matToBitmap(mat1, bt3);
		iv3.setImageBitmap(bt3);
			
		}

}

处理上  bitmap  与mat 的 一定要注意 图片的宽高一致不然容易 Exception

/cv::error()(17079): OpenCV Error: Assertion failed (src.dims == 2 && info.height == (uint32_t)src.rows && info.width == 

(uint32_t)src.cols) in void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean), file 

/home/reports/ci/slave/50-SDK/opencv/modules/java/generator/src/cpp/utils.cpp, line 97

/org.opencv.android.Utils(17079): nMatToBitmap catched cv::Exception: /home/reports/ci/slave/50-

SDK/opencv/modules/java/generator/src/cpp/utils.cpp:97: error: (-215) src.dims == 2 && info.height == (uint32_t)src.rows && 

info.width == (uint32_t)src.cols in function void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, 

jobject, jboolean)