java-Android day06

Android Day03

by 木石溪

今天被實驗室大佬抓住，說我在不幹正事，讓寫個灰度直方圖均衡化的攝像Demo，
怎麼可能屈服在他淫威下，我寫還不行。。。慫~~

實現思路：

• Part1：調用攝像頭
  1. 動態授權；
  2. 設置拍照意圖，啓動拍照；
• Part2：圖片處理
  3. 進行圖像二值化；
  4. 進行灰度直方圖均衡化；
  5. 顯示處理圖片；

step1：界面（按鍵 + 均衡化顯示）

主要部件：

• 拍照 Button
• 圖片顯示 ImageView

    <?xml version="1.0" encoding="utf-8"?>
   <android.support.constraint.ConstraintLayout
            xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            xmlns:app="http://schemas.android.com/apk/res-auto"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="horizontal"
            tools:ignore="TableFor"
            tools:context=".MainActivity">
    
        <Button android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:id="@+id/bt_camera"
                android:text="@string/bt_camera"
                app:layout_constraintTop_toTopOf="parent" app:layout_constraintStart_toStartOf="@+id/imageView"
                android:layout_marginBottom="3dp" app:layout_constraintBottom_toTopOf="@+id/imageView"/>
        <ImageView android:layout_width="0dp" android:layout_height="0dp"
                   android:id="@+id/imageView" app:layout_constraintTop_toBottomOf="@+id/bt_camera"
                   android:layout_marginBottom="2dp" app:layout_constraintEnd_toEndOf="parent"
                   app:layout_constraintStart_toStartOf="parent" app:layout_constraintBottom_toBottomOf="parent"/>
    
    </android.support.constraint.ConstraintLayout>

Step2：實現攝像頭動態授權和調用

Part01 : 設置按鍵監聽

	// load layout and find view parts by id
	setContentView(R.layout.activity_main);
	Button bt_camera = findViewById(R.id.bt_camera);
	mMImageView = findViewById(R.id.imageView);

	// set listener of button clicked
	bt_camera.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.CAMERA}, MY_PERMISSION_REQUEST_CODE);
                } else {
                    takePhoto();
                }
            }
        });

Part02: 進行M 運行權限授權

	@Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode) {
            case MY_PERMISSION_REQUEST_CODE:
                if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    takePhoto();
                } else {
                    Toast.makeText(this, "THE PERMISSION DENIED", Toast.LENGTH_SHORT).show();
                }
            default:
                super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

Part03：設置拍照程序

	private void takePhoto() {
		Intent photo_act = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        startActivityForResult(photo_act, TAKE_PHOTO_CODE);
	}

	@Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (resultCode == RESULT_OK) {
            switch (requestCode) {
                case TAKE_PHOTO_CODE:
                    Bundle extras = data.getExtras();
                    Bitmap imageBitmap = (Bitmap) extras.get("data");
            		
            		// digital image processing
            		Bitmap dst = equalize(imageBitmap);
            		mImageView.setImageBitmap(dst);
                    break;
                default:
                    break;
            }
        }
   }

Part04： 圖像二值化和直方圖均衡化處理

	//--------------------------------------
   // Digital Image Processing
   //--------------------------------------
   private Bitmap equalize(Bitmap src){
   
       // 1. convert Bitmap to color array
       int rows = src.getHeight();
       int cols = src.getWidth();
       int size = rows * cols;
       int[] img = new int[rows * cols];
       
       // each element of color array is a PACKED color code for that pixel, which can be decomposed to A,R,G and B
       src.getPixels(img,0,cols,0,0,cols,rows);
       
       // 2. convert ARGB/RGB color code 2 Gray Scale and calculate image histogram
       // since we've already allocated a int array for all the pixels, there's no need to allocated another 'uchar' for them
       int base,id,color,level,r,c = 0;
       int[] hist = new int[256];
       for(r=0; r<rows; r++){
           base = r*cols;
           for(c=0; c<cols; c++){
               id = base + c;
               color = img[id];
               level = (int)Math.round((0.299 * Color.red(color) + 0.587 * Color.green(color) + 0.114 * Color.blue(color)));
               img[id] = level;
               // calculate histogram at the same time
               hist[level]++;
           }
       }
       
       // 3. get PDF
       double[] pdf = new double[256];
       for(int i=0; i<256; i++){
           pdf[i] = (double)hist[i]/size;
       }
       
       // 4. get CDF and generate dictionary
       int[] dict = new int[256];
       double tmpd = 0;
       for(int m=0; m<256; m++){
           tmpd = 0;
           for(int n=0; n<=m; n++){
               tmpd += pdf[n];
           }
           dict[m] = (int)Math.round(255*tmpd);
       }
       
       // 5. map img back to color code using dictionary
       for(r=0; r<rows; r++){
           base = r*cols;
           for(c=0; c<cols; c++){
               id = base + c;
               level = dict[img[id]];
               img[id] = Color.rgb(level,level,level);
           }
       }
       System.out.println(dict[200] + ", " + dict[201] + ", " + dict[202]);
       System.out.println(img[200] + ", " + img[201] + ", " + img[202]);

       // 6. set Bitmap
       return Bitmap.createBitmap(img,cols,rows,src.getConfig());
   }

結果：

未解決問題

1. 目前處理圖片爲略縮圖，圖像清晰度不夠；
2. 灰度直方圖均衡化算法有待提升；