code: private void drawFlippingShadeShine(Canvas canvas) {
  		final float degreesFlipped = getDegreesFlipped();
  		if (degreesFlipped < 90) {
  			final int alpha = (int) ((degreesFlipped / 90f) * MAX_SHINE_ALPHA);
  			mShinePaint.setAlpha(alpha);
  			canvas.drawRect(isFlippingVertically() ? mBottomRect : mRightRect,
  					mShinePaint);
  		} else {
  			final int alpha = (int) ((Math.abs(degreesFlipped - 180) / 90f) * MAX_SHADE_ALPHA);
  			mShadePaint.setAlpha(alpha);
  			canvas.drawRect(isFlippingVertically() ? mTopRect : mLeftRect,
  					mShadePaint);
  		}
  	}
docs: will draw a shade if flipping on the previous(top/left) half and a shine
  if flipping on the next(bottom/right) half
  
  @param canvas