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)