Android Bitmap

時間 2019-11-16

標籤 android bitmap 欄目 Android 简体版

原文原文鏈接

一圖片表示原理git

圖片是由每一個像素點來組成像素點就是小方塊github

圖片的大小等於寬*高*每一個像素點的大小canvas

二加載圖片OOM異常dom

解決辦法 ide

其中big.jpg是一張21.2MB的高清圖工具

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    ImageView mImageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViewById(R.id.load).setOnClickListener(this);
        mImageView = findViewById(R.id.image);
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.load:
                load();
                break;
        }
    }

    private void load() {
        try {
            BitmapFactory.Options option = new BitmapFactory.Options();
            option.inJustDecodeBounds = true; //只會解析圖片的大小 不會加載圖片的內容
            BitmapFactory.decodeStream(getAssets().open("big.jpg"), null, option);
            // 獲取圖片的寬高
            int width = option.outWidth;
            int height = option.outHeight;
            // 獲取屏幕的寬高
            int screenWidth = getScreenWidth();
            int screenHeight = getScreenHeight();
            // 把圖片的寬高和屏幕的寬高進行對比
            int scaleX = width / screenWidth;
            int scaleY = height / screenHeight;
            int scale = scaleX > scaleY ? scaleX : scaleY;
            option.inJustDecodeBounds = false; //加載圖片的內容
            // 若是設置爲>1 請求解碼器對原始數據進行子採樣 例如inSampleSize==4返回圖像的寬度/高度是原始圖像的1/4
            // 任何值<=1都與1相同
            option.inSampleSize = scale;
            Bitmap bitmap = BitmapFactory.decodeStream(getAssets().open("big.jpg"), null, option);
            int byteCount = bitmap.getByteCount();
            Log.i("HUANG", "byteCount=" + byteCount);
            mImageView.setImageBitmap(bitmap);

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

    /** 獲得設備屏幕的寬度 (像素) **/
    private int getScreenWidth() {
        return getResources().getDisplayMetrics().widthPixels;
    }

    /** 獲得設備屏幕的高度 (像素) **/
    private int getScreenHeight() {
        return getResources().getDisplayMetrics().heightPixels;
    }

}

三圖片處理原理this

Android裏面全部的顯示效果都是繪製出來的spa

用Android封裝好的繪圖類去繪製圖片code

Canvas: 畫布對象

Paint: 畫筆

Matrix: 圖形矩陣 3*3

Bitmap: 要繪製的圖片

四圖片的旋轉平移縮放

其中mm.jpg是一張57KB的圖屬於正常範圍不須要額外處理

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    ImageView mImageView, mCopyView;
    Bitmap mBitmap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findViewById(R.id.change).setOnClickListener(this);
        mImageView = findViewById(R.id.image);
        mCopyView = findViewById(R.id.copy);
        try {
            mBitmap = BitmapFactory.decodeStream(getAssets().open("mm.jpg"));
            mImageView.setImageBitmap(mBitmap);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.change:
                change();
                break;
        }
    }

    // 圖片的旋轉 平移 縮放
    // 注意: 旋轉 平移 縮放 這三種效果在本案例中只能同時存在一種 分別打開註釋看效果
    private void change() {
        if (null == mBitmap) return;
        // 新建空白的圖片 要和原圖的大小同樣
        Bitmap bitmap = Bitmap.createBitmap(mBitmap.getWidth(), mBitmap.getHeight(), mBitmap.getConfig());
        Canvas canvas = new Canvas(bitmap); //畫布 傳參必須是一個空白的圖片 不然報錯
        Paint paint = new Paint(); //畫筆
        Matrix matrix = new Matrix(); //矩陣
        // 旋轉30度 以圖片的中心爲圓心
        matrix.setRotate(30, mBitmap.getWidth() / 2, mBitmap.getHeight() / 2);
        // X軸平移80
        //matrix.setTranslate(80, 0);
        // Y軸縮爲原來的0.5
        //matrix.setScale(1F, 0.5F, mBitmap.getWidth() / 2, mBitmap.getHeight() / 2);
        canvas.drawColor(Color.WHITE); //繪製背景爲白色
        canvas.drawBitmap(mBitmap, matrix, paint); //繪製圖片
        mCopyView.setImageBitmap(bitmap);
    }

}

五圖片的塗鴉操做

其中mm.jpg是一張57KB的圖屬於正常範圍不須要額外處理

public class MainActivity extends AppCompatActivity implements View.OnTouchListener {

    ImageView mImageView;
    Bitmap mNewBitmap;
    Canvas mCanvas;
    Paint mPaint;
    Matrix mMatrix;
    int mStartX, mStartY; //按下點的座標

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mImageView = findViewById(R.id.image);
        try {
            Bitmap bitmap = BitmapFactory.decodeStream(getAssets().open("mm.jpg"));
            // 不能直接在原圖上進行繪製 必須新建空白的圖片
            mNewBitmap = Bitmap.createBitmap(bitmap.getWidth(), bitmap.getHeight(), bitmap.getConfig());
            mCanvas = new Canvas(mNewBitmap);
            mPaint = new Paint();
            mPaint.setColor(Color.YELLOW);
            mMatrix = new Matrix();
            // 把原圖繪製在空白的圖片上
            mCanvas.drawBitmap(bitmap, mMatrix, mPaint);
            mImageView.setImageBitmap(mNewBitmap);
            mImageView.setOnTouchListener(this); //設置觸摸監聽

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

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN: //按下
                mStartX = (int) event.getX();
                mStartY = (int) event.getY();
                break;

            case MotionEvent.ACTION_MOVE: //移動
                // 獲取移動點的座標
                int moveX = (int) event.getX();
                int moveY = (int) event.getY();
                // 畫線
                mCanvas.drawLine(mStartX, mStartY, moveX, moveY, mPaint);
                // 把新圖設置給ImageView
                mImageView.setImageBitmap(mNewBitmap);
                // 把移動點置爲開始點
                mStartX = moveX;
                mStartY = moveY;
                break;

            case MotionEvent.ACTION_UP: //彈起
                break;
        }
        return true; //事件本身來處理
    }

}

六圖片的顏色處理

圖片是有顏色

核心原理就是重繪圖片

改變圖片的顏色就是對畫筆進行操

其中mm.jpg是一張57KB的圖屬於正常範圍不須要額外處理

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    ImageView mImageView;
    Bitmap mBitmap, mNewBitmap;
    Canvas mCanvas;
    Paint mPaint;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mImageView = findViewById(R.id.image);
        try {
            mBitmap = BitmapFactory.decodeStream(getAssets().open("mm.jpg"));
            mImageView.setImageBitmap(mBitmap);
            mNewBitmap = Bitmap.createBitmap(mBitmap.getWidth(), mBitmap.getHeight(), mBitmap.getConfig());
            mCanvas = new Canvas(mNewBitmap);
            mPaint = new Paint();
            findViewById(R.id.change).setOnClickListener(this);

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

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.change:
                int randomR = (int) (Math.random() * 256); //0-255 隨機數
                int randomG = (int) (Math.random() * 256); //0-255 隨機數
                int randomB = (int) (Math.random() * 256); //0-255 隨機數
                int randomA = (int) (Math.random() * 256); //0-255 隨機數
                float colorR = (255 - randomR) / (float) 255;
                float colorG = (255 - randomG) / (float) 255;
                float colorB = (255 - randomB) / (float) 255;
                float colorA = (255 - randomA) / (float) 255;
                Log.i("HUANG", "randomR=" + randomR);
                Log.i("HUANG", "randomG=" + randomG);
                Log.i("HUANG", "randomB=" + randomB);
                Log.i("HUANG", "randomA=" + randomA);
                Log.i("HUANG", "colorR=" + colorR);
                Log.i("HUANG", "colorG=" + colorG);
                Log.i("HUANG", "colorB=" + colorB);
                Log.i("HUANG", "colorA=" + colorA);

                ColorMatrix matrix = new ColorMatrix(); //顏色矩陣 5*4
                matrix.set(new float[]{
                        colorR, 0, 0, 0, 0, //red
                        0, colorG, 0, 0, 0, //green
                        0, 0, colorB, 0, 0, //blue
                        0, 0, 0, colorA, 0 //alpha
                });
                ColorMatrixColorFilter filter = new ColorMatrixColorFilter(matrix);
                mPaint.setColorFilter(filter);
                mCanvas.drawBitmap(mBitmap, new Matrix(), mPaint);
                mImageView.setImageBitmap(mNewBitmap);
                break;
        }
    }

}