增加文字描边

重写UILabel的drawTextInRect方法

//增加描边属性
@property (strong, nonatomic) UIColor *stokeColor;
@property (assign, nonatomic) CGFloat strokeWidth;

- (void)drawTextInRect:(CGRect)rect {
    
    CGSize shadowOffset = self.shadowOffset;
    UIColor *textColor = self.textColor;
    
    CGContextRef c = UIGraphicsGetCurrentContext();
    CGContextSetLineWidth(c, self.strokeWidth);
    CGContextSetLineJoin(c, kCGLineJoinRound);
    
    CGContextSetTextDrawingMode(c, kCGTextStroke);
    self.textColor = self.stokeColor;
    [super drawTextInRect:rect];
    
    CGContextSetTextDrawingMode(c, kCGTextFill);
    self.textColor = textColor;
    self.shadowOffset = CGSizeMake(0, 0);
    [super drawTextInRect:rect];
    
    self.shadowOffset = shadowOffset;
    
}