code show as below

-(void) drawRect:(CGRect)rect{
//CGContextRef context = UIGraphicsGetCurrentContext();
//CGContextSetRGBFillColor(context, 0.0, 0.0, 0.0, 0.2);
[[UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.2]setFill];
CGRect grayRect = self.frame;
UIRectFill(grayRect);

CGRect cropRect = _intersectionRect;
CGRect intersectionRect = CGRectIntersection(cropRect, grayRect);
[[UIColor clearColor]setFill];
UIRectFill(intersectionRect);
}

In the demo of the blank project, everything is ok

But in my own project, there are extra 1px and borders with different transparency. How to solve it?