使用Android-OpenCV

在這篇文章中提到如建立Android-OpenCV環境.
接下來開始使用Android-OpenCV

1.開啟Eclipse進入Workspace "android-opencv240".
2.進入我們的第一個專案, 開啟MyFirstAndroidOpenCV.java檔案.

3.使用OpenCV的canny()做為範例.
4.先準備原始圖

5.將此檔案放入專案目錄中的3個目錄
   \android-opencv240\MyFirstAndroidOpenCV\res\drawable-hdpi
   \android-opencv240\MyFirstAndroidOpenCV\res\drawable-ldpi
   \android-opencv240\MyFirstAndroidOpenCV\res\drawable-mdpi
  之所以會有3個目錄, 是因為Android會根據手機的螢幕密度(density)來取得圖片,
  如果不在意的話, 3個全放就萬無一失, 想再深入了解可參考此連結.

6.這篇文章主要是簡單介紹如何使用Android-OpenCV, 所以就不處理顯示的部份,
  整個程式流程就是讀檔->Canny()處理->寫檔.

7.遇到Java不認識的類別時, 就手動import.

8.程式碼

package my.project.MyFirstAndroidOpenCV;

import java.io.FileOutputStream;
import java.io.InputStream;

import org.opencv.android.Utils;
import org.opencv.core.Mat;
import org.opencv.imgproc.Imgproc;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;

public class MyFirstAndroidOpenCV extends Activity 
{
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        // read image from resource
        InputStream is = this.getResources().openRawResource(R.drawable.foot);
        Bitmap footbm = BitmapFactory.decodeStream(is);
        
        Mat footMat = new Mat();
        //convert bitmap to opencv Mat 
        Utils.bitmapToMat(footbm, footMat);
        
        //Convert to Gray image
        Mat footGrayMat = new Mat();
        Imgproc.cvtColor(footMat, footGrayMat, Imgproc.COLOR_BGR2GRAY, 1);
        
        //Do canny
        Mat outCannyMat = new Mat();
        Imgproc.Canny(footGrayMat, outCannyMat, 80, 100, 3, false);
 
        //output to file
        OutputGrayMatToFile(outCannyMat, "Canny");
    }
    
private void OutputGrayMatToFile(Mat mGaryMat, String Filename)
{
    Mat mRgba = new Mat();
    Imgproc.cvtColor(mGaryMat, mRgba, Imgproc.COLOR_GRAY2BGRA, 4);
    Bitmap bmp = Bitmap.createBitmap(mRgba.cols(), mRgba.rows(), Bitmap.Config.ARGB_8888);
    Utils.matToBitmap(mRgba, bmp);
  
    try 
    {
       FileOutputStream out = new FileOutputStream("/mnt/sdcard/"+Filename+".png");
        bmp.compress(Bitmap.CompressFormat.PNG, 90, out);  
    } 
    catch (Exception e) 
    {
        e.printStackTrace();
    }
}
    
}

9. 因為有寫檔案到sdcard, 所以需要將此權限開啟, 編輯AndroidManifest.xml

10.產生的檔案會在/mnt/sdcard/canny.png