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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(); }

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