如何获得总覆盖面积，同时绘制在画布上的android路径？

问题描述

即时通讯使用低于code画上，而手指触摸的举动......我在这里公布的部分code，这是工作的罚款..位帆布行

如下面的图像，黑白位图抹去触摸拖动。我帆布制成透明的，所以家长布局背景（彩色图像）越来越明显。

我想知道，有多少面积被删除（如50％或位图的60％）..有没有办法找到？

  //删除油漆

         mDrawPaint =新的油漆（）;
    mDrawPaint.setAntiAlias​​（真正的）;
    mDrawPaint.setDither（真正的）;
    mDrawPaint.setStyle（Paint.Style.STROKE）;
    mDrawPaint.setStrokeJoin（Paint.Join.ROUND）;
    mDrawPaint.setStrokeCap​​（Paint.Cap.ROUND）;
    mDrawPaint.setStrokeWidth（50）;
    mDrawPaint.setXfermode（新PorterDuffXfermode（PorterDuff.Mode.CLEAR））;
    BlurMaskFilter运动模糊=新BlurMaskFilter（10，BlurMaskFilter.Blur.NORMAL）;
    mDrawPaint.setMaskFilter（运动模糊）;
 

---

 私人无效doDraw（帆布C）{

    c.drawBitmap（mBitmap，0，0，NULL）;

}
 

---

 私人浮动MX，我的;
私有静态最终浮动TOUCH_TOLERANCE = 1;

无效touch_start（浮X，浮动Y）{
    mPath.reset（）;
    mPath.moveTo（X，Y）;
    MX = X;
    我= Y;
}
无效TOUCH_MOVE（浮X，浮动Y）{
    浮DX = Math.abs（X  -  MX）;
    浮DY = Math.abs（Y  - 我的）;
    如果（DX＆GT; = TOUCH_TOLERANCE || DY＆GT; = TOUCH_TOLERANCE）{
        mPath.quadTo（MX，MY，（X + MX）/ 2，（Y +我）/ 2）;
        MX = X;
        我= Y;
    }

     canvas.drawPath（的mpath，mDrawPaint）; //删除黑白图像

}
无效touch_up（）{
    mPath.lineTo（MX，MY）;
    //提交路径，我们的屏幕外
    mCanvas.drawPath（的mpath，mDrawPaint）;
    //杀了这个，所以我们不重复抽奖
    mPath.reset（）;
}
 

解决方案

尝试使用蒙特卡罗方法估计百分比的透明区域。我认为这是做这是一个最快，最简单的方法。取约50（取决于精度需要）随机像素上的透明面罩，并检查它们的颜色。然后计算ANS = TransparentPixelsCount / TestPixelCount。

这是很难计算使用路径坐标用户的图纸广场。这是相当长的遍历所有像素。因此，恕我直言蒙特卡洛是您最佳的选择。

Im using below code to draw line on bitmap canvas while finger touch move... here i posted partial code and it is working fine..

As shown in below image, the black and white bitmap erased on touch drag.. I made canvas transparent so the parent layout background(color image) is getting visible.

I want to know , how much area is erased(like 50% or 60% of bitmap ).. is there any way to find that?

//Erasing paint

         mDrawPaint = new Paint();
    mDrawPaint.setAntiAlias(true);
    mDrawPaint.setDither(true);
    mDrawPaint.setStyle(Paint.Style.STROKE);
    mDrawPaint.setStrokeJoin(Paint.Join.ROUND);
    mDrawPaint.setStrokeCap(Paint.Cap.ROUND);
    mDrawPaint.setStrokeWidth(50);
    mDrawPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
    BlurMaskFilter mBlur = new BlurMaskFilter(10, BlurMaskFilter.Blur.NORMAL);
    mDrawPaint.setMaskFilter(mBlur);

---

private void doDraw(Canvas c) {

    c.drawBitmap(mBitmap, 0, 0,null );

}

---

private float mX, mY;
private static final float TOUCH_TOLERANCE = 1;

void touch_start(float x, float y) {
    mPath.reset();
    mPath.moveTo(x, y);
    mX = x;
    mY = y;
}
void touch_move(float x, float y) {
    float dx = Math.abs(x - mX);
    float dy = Math.abs(y - mY);
    if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
        mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
        mX = x;
        mY = y;
    }

     canvas.drawPath(mPath, mDrawPaint ); //Erasing Black and white image

}
void touch_up() {
    mPath.lineTo(mX, mY);
    // commit the path to our offscreen
    mCanvas.drawPath(mPath, mDrawPaint);
    // kill this so we don't double draw
    mPath.reset();
}

解决方案

Try to use Monte Carlo method to estimate percentage of transparent area. I think it is a fastest and easiest way to do this. Take about 50 (depends on accuracy you need) random pixels on your transparency mask and check their color. Then calc ans = TransparentPixelsCount/TestPixelCount.

It is very hard to calculate square of user's drawings using path coordinates. And it's quite long to iterate over all pixels. So, IMHO Monte Carlo is your choise.

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