package cn.edu.zju.myopencv;

import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

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

import java.io.InputStream;

public class JavaActivity extends AppCompatActivity {



// Used to load the 'native-lib' library on application startup.
static {
System.loadLibrary("native-lib");
    }


private double max_size = 1024;
private int PICK_IMAGE_REQUEST = 1;
private ImageView myImageView;
private Bitmap selectbp;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_java);
staticLoadCVLibraries();
myImageView = (ImageView)findViewById(R.id.imageView);
myImageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
Button selectImageBtn = (Button)findViewById(R.id.select_btn);
selectImageBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// makeText(MainActivity.this.getApplicationContext(), "start to browser image", Toast.LENGTH_SHORT).show();
selectImage();
            }

private void selectImage() {
Intent intent = new Intent();
intent.setType("image/*");
intent.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(Intent.createChooser(intent,"選擇圖像..."), PICK_IMAGE_REQUEST);
            }
        });

Button processBtn = (Button)findViewById(R.id.process_btn);
processBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// makeText(MainActivity.this.getApplicationContext(), "hello, image process", Toast.LENGTH_SHORT).show();
convertGray();
            }
        });

    }

private void staticLoadCVLibraries() {
boolean load = OpenCVLoader.initDebug();
if(load) {
Log.i("CV", "Open CV Libraries loaded...");
        }

    }

private void convertGray() {
Mat src = new Mat();
Mat temp = new Mat();
Mat dst = new Mat();
Utils.bitmapToMat(selectbp, src);
Imgproc.cvtColor(src, temp, Imgproc.COLOR_BGRA2BGR);
Log.i("CV", "image type:" + (temp.type() == CvType.CV_8UC3));
Imgproc.cvtColor(temp, dst, Imgproc.COLOR_BGR2GRAY);
Utils.matToBitmap(dst, selectbp);
myImageView.setImageBitmap(selectbp);
    }


@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if(requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK && data != null && data.getData() != null) {
Uri uri = data.getData();
try {
Log.d("image-tag", "start to decode selected image now...");
InputStream input = getContentResolver().openInputStream(uri);
BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeStream(input, null, options);
int raw_width = options.outWidth;
int raw_height = options.outHeight;
int max = Math.max(raw_width, raw_height);
int newWidth = raw_width;
int newHeight = raw_height;
int inSampleSize = 1;
if(max > max_size) {
newWidth = raw_width / 2;
newHeight = raw_height / 2;
while((newWidth/inSampleSize) > max_size || (newHeight/inSampleSize) > max_size) {
inSampleSize *=2;
                    }
                }

options.inSampleSize = inSampleSize;
options.inJustDecodeBounds = false;
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
selectbp = BitmapFactory.decodeStream(getContentResolver().openInputStream(uri), null, options);

myImageView.setImageBitmap(selectbp);

            } catch (Exception e) {
e.printStackTrace();
            }
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_java"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="cn.edu.zju.myopencv.JavaActivity"
android:orientation="vertical"
>

<Button
android:id="@+id/select_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="選擇圖片" />

<Button
android:id="@+id/process_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="處理" />

<ImageView
android:id="@+id/imageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />

</LinearLayout>