一、 UIImageView 分类

.h
/// 绘制多边形
/// @param lineWidth 线宽
/// @param lineColor 线颜色
/// @param sides 边数
/// @param cornerRadius 圆角
- (void)eh_drawSexangleImageViewLineWidth:(CGFloat)lineWidth
                                lineColor:(UIColor *)lineColor
                                    sides:(NSUInteger)sides
                             cornerRadius:(CGFloat)cornerRadius;
                             
.m
/// 绘制多边形
/// @param lineWidth 线宽
/// @param lineColor 线颜色
/// @param sides 边数
/// @param cornerRadius 圆角
- (void)eh_drawSexangleImageViewLineWidth:(CGFloat)lineWidth
                                lineColor:(UIColor *)lineColor
                                    sides:(NSUInteger)sides
                             cornerRadius:(CGFloat)cornerRadius {
    UIBezierPath *path   = [UIBezierPath eh_polygonInRect:self.bounds
                                                    sides:sides
                                                linewidth:lineWidth
                                             cornerRadius:cornerRadius];
     
    // mask for the image view
    CAShapeLayer *mask   = [CAShapeLayer layer];
    mask.path            = path.CGPath;
    mask.lineWidth       = lineWidth;
    mask.strokeColor     = [UIColor clearColor].CGColor;
    mask.fillColor       = [UIColor whiteColor].CGColor;
    self.layer.mask = mask;
     
    // if you also want a border,add that as a separate layer
     
    CAShapeLayer *border = [CAShapeLayer layer];
    border.path          = path.CGPath;
    border.lineWidth     = lineWidth;
    border.strokeColor   = lineColor.CGColor;
    border.fillColor     = [UIColor clearColor].CGColor;
    [self.layer addSublayer:border];
}

二、UIBezierPath 分类

.h
/** Create UIBezierPath for regular polygon with rounded corners
 *
 * @param rect          The CGRect of the square in which the path should be created.
 * @param sides         How many sides to the polygon (e.g. 6=hexagon; 8=octagon,etc.).
 * @param linewidth     The width of the stroke around the polygon. The polygon will be inset such that the stroke stays within the above square.
 * @param cornerRadius  The radius to be applied when rounding the corners.
 *
 * @return              UIBezierPath of the resulting rounded polygon path.
 */
 
+ (instancetype)eh_polygonInRect:(CGRect)rect
                           sides:(NSInteger)sides
                       linewidth:(CGFloat)linewidth
                    cornerRadius:(CGFloat)cornerRadius;
                    
                    
.m
+ (instancetype)eh_polygonInRect:(CGRect)rect
                           sides:(NSInteger)sides
                       linewidth:(CGFloat)linewidth
                    cornerRadius:(CGFloat)cornerRadius {
    UIBezierPath *path  = [UIBezierPath bezierPath];
 
    CGFloat theta       = 2.0 * M_PI / sides;                           // how much to turn at every corner
    CGFloat offset      = cornerRadius * tanf(theta / 2.0);             // offset from which to start rounding corners
    CGFloat squareWidth = MIN(rect.size.width,rect.size.height);   // width of the square
 
    // calculate the length of the sides of the polygon
 
    CGFloat length      = squareWidth - linewidth;
    if (sides % 4 != 0) {                                               // if not dealing with polygon which will be square with all sides ...
        length = length * cosf(theta / 2.0) + offset/2.0;               // ... offset it inside a circle inside the square
    }
    CGFloat sideLength = length * tanf(theta / 2.0);
 
    // start drawing at `point` in lower right corner
 
    CGPoint point = CGPointMake(rect.origin.x + rect.size.width / 2.0 + sideLength / 2.0 - offset,rect.origin.y + rect.size.height / 2.0 + length / 2.0);
    CGFloat angle = M_PI;
    [path moveToPoint:point];
 
    // draw the sides and rounded corners of the polygon
 
    for (NSInteger side = 0; side < sides; side++) {
        point = CGPointMake(point.x + (sideLength - offset * 2.0) * cosf(angle),point.y + (sideLength - offset * 2.0) * sinf(angle));
        [path addLineToPoint:point];
 
        CGPoint center = CGPointMake(point.x + cornerRadius * cosf(angle + M_PI_2),point.y + cornerRadius * sinf(angle + M_PI_2));
        [path addArcWithCenter:center radius:cornerRadius startAngle:angle - M_PI_2 endAngle:angle + theta - M_PI_2 clockwise:YES];
 
        point = path.currentPoint; // we don't have to calculate where the arc ended ... UIBezierPath did that for us
        angle += theta;
    }
 
    [path closePath];
 
    path.lineWidth = linewidth;           // in case we're going to use CoreGraphics to stroke path,rather than CAShapeLayer
    path.lineJoinStyle = kCGLineJoinRound;
 
    return path;
}

三、用法

[self.headBgImageView eh_drawSexangleImageViewLineWidth:3.0 lineColor:UIColorFromRGB(0xFFFFFF) sides:6 cornerRadius:8.0];