android– 通过触摸输入在位图上绘制透明线[复制]

概述参见英文答案>MakingOverlaidimagetransparentontouchinAndroid?                                    3个我正在开发Android的绘图应用程序.现在我想实现一个橡皮擦,允许通过使用触摸输入擦除加载的位图的部分,并使位图沿手指的路

参见英文答案 > Making Overlaid image transparent on touch in Android?                                    3个
我正在开发AndroID的绘图应用程序.现在我想实现一个橡皮擦,允许通过使用触摸输入擦除加载的位图的部分,并使位图沿手指的路径透明.

我尝试实现的一个很好的例子显示在AndroID应用程序Steamy Window中. Steamy Window模拟雾化窗口,用户可以通过触摸输入擦除部分雾.

有关我如何实现该功能的任何建议？

更新：我在下面发布了当前代码中最重要的部分.由于以下原因,我对它并不满意：

>绘画相当迟钝.我可以在这里改进什么？
>我正在寻找一种方法来使用Alpha蒙版来设置像素的像素透明度/ Alpha,因为我想模拟画笔.有任何建议如何实现这一目标？

        public DrawVIEw(Context context, String imagename) {        super(context);        // Get the overlay image and its dimensions        Bitmap overlayImageOriginal = BitmapFactory.decodeResource(                getResources(), R.drawable.overlay);        wIDth = overlayImageOriginal.getWIDth();        height = overlayImageOriginal.getHeight();        // Get a copy of the overlay image and recycle the original        overlayImage = overlayImageOriginal.copy(Config.ARGB_8888, true);        overlayImageOriginal.recycle();        // Get background image of this level        int resID = getResources().getIDentifIEr(imagename, "drawable",                "com.xxx");        backgroundImage = BitmapFactory.decodeResource(getResources(), resID);        // copy pixels        overlayImagePixels = new int[wIDth * height];        overlayImage.getPixels(overlayImagePixels, 0, wIDth, 0, 0, wIDth,                height);        getHolder().addCallback(this);        _thread = new DrawThread(getHolder(), this);        setFocusable(true);    }    @OverrIDe    public boolean ontouchEvent(MotionEvent event) {        synchronized (_thread.getSurfaceHolder()) {            switch (event.getAction()) {            case MotionEvent.ACTION_DOWN:                touchstart(event.getX(), event.getY());                return true;            case MotionEvent.ACTION_MOVE:                touchmove(event.getX(), event.getY());                return true;            case MotionEvent.ACTION_UP:                touchStop();                return true;            }            return false;        }    }    @OverrIDe    public voID onDraw(Canvas canvas) {       // draw the image to guess       canvas.drawBitmap(backgroundImage, 0, 0, null);       // apply user input to the overlay-image       setRegionTransparency((int) mtouchX, (int) mtouchY, 20, 0);       // draw the overlay-image (hIDing the image to guess)       canvas.drawBitmap(overlayImage, 0, 0, null);    }    /**     *      * @param posX     * @param posY     * @param radius     * @param Alpha - 0: full transparent, 255: full opaque     */    private voID setRegionTransparency(int posX, int posY, int radius, int Alpha) {        int left = posX - radius;        int right = posX + radius;        int top = posY - radius;        int bottom = posY + radius;        int color = 0;        // onDraw() is called before any user input        // -> assume 0/0 as invalID arguments        if (posX == 0 && posY == 0) {              return;        }        // Todo currently only rectangular area is supported        // but we need circular        // we should use a pre-made Alpha mask with smoothed edges        // we should take into account: pressure and/or duration of touch        for (int y = top; y = 0 && y = 0 && x = touch_TolERANCE || dy >= touch_TolERANCE) {            mPath.quadTo(mtouchX, mtouchY, (x + mtouchX) / 2, (y + mtouchY) / 2);            mtouchX = x;            mtouchY = y;        }    }}

解决方法:

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Making Overlaid image transparent on touch in Android?

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