ios设置文本的边框颜色

/**
 空心字体

 @param str 文本
 @param textColor 文本颜色
 @param textBorderColor 文本边框颜色
 @param strokeWidth 文件边框宽度
 @return 文本
 */
+(NSMutableAttributedString *)textHollow:(NSString *)str textColor:(UIColor *)textColor textBorderColor:(UIColor *)textBorderColor strokeWidth:(CGFloat)strokeWidth
{
    NSDictionary *dict = @{
                           NSStrokeColorAttributeName:textBorderColor,
                           NSStrokeWidthAttributeName : [NSNumber numberWithFloat:strokeWidth],
                           NSForegroundColorAttributeName:textColor
                           };
    NSMutableAttributedString *attribtStr = [[NSMutableAttributedString alloc] initWithString:str attributes:dict];
    return attribtStr;
}

self.progressLabel.attributedText = [NSString textHollow:[NSString stringWithFormat:@"%.0f",progress] textColor:_progressColor textBorderColor:[UIColor lightGrayColor] strokeWidth:-3];