Android Bitmap 倒影

   

public Bitmap invertedImg() {
    //1. 倒立图
    Matrix matrix = new Matrix();
    matrix.preScale(1, -1);
    int w = mBitmap.getWidth();
    int h = mBitmap.getHeight();
    Bitmap reflectionImg = Bitmap.createBitmap(mBitmap, 0, h / 2, w, h / 2, matrix, false);

    //2. 要生成原图加倒立图，先生成一个可变的Bitmap，高度为1.5倍原h
    int gap = 10; //间隙 空白
    Bitmap newBitmap = Bitmap.createBitmap(w, h + h / 2 + gap, Bitmap.Config.ARGB_8888);
    Paint paint = new Paint();
    Canvas canvas = new Canvas(newBitmap);
    canvas.drawBitmap(mBitmap, 0, 0, paint);  //绘制原图
    canvas.drawBitmap(reflectionImg, 0, h + gap, paint); //绘制倒立图

    //3. 画笔使用 LinearGradient 线性渐变渲染
    LinearGradient lg = new LinearGradient(0, h + gap, w, newBitmap.getHeight(), 0xabff0000,
            0x00ffff00, Shader.TileMode.MIRROR);
    paint.setShader(lg);

    //4. 指定画笔的Xfermode  即绘制的模式(不同的模式，绘制的区域不同)
    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_ATOP));

    //5. 在倒立图区，绘制矩形渲染图层
    canvas.drawRect(0, h + gap, w, newBitmap.getHeight(), paint);
    paint.setXfermode(null);

    return newBitmap;
}