@interface UIImage (PPRoundedAvatar)
/**
 将图片进行圆角处理，默认无边框
 */
- (nullable UIImage *)pp_imageByRoundCornerRadius:(CGFloat)radius
                                        scaleSize:(CGSize)newSize;
/**
 将图片进行圆角处理，并加上边框
 */
- (nullable UIImage *)pp_imageByRoundCornerRadius:(CGFloat)radius
                                        scaleSize:(CGSize)newSize
                                      borderWidth:(CGFloat)borderWidth
                                      borderColor:(nullable UIColor *)borderColor;
/**
 图片加上圆形边框，图片必须得是正方形的，否则直接返回未加边框的原图片
 */
- (nullable UIImage *)pp_imageByRoundBorderedColor:(nullable UIColor *)color
                                       borderWidth:(CGFloat)width;
@end

// 图片圆角裁剪
- (UIImage *)pp_imageByRoundCornerRadius:(CGFloat)radius
                             borderWidth:(CGFloat)borderWidth
                             borderColor:(UIColor *)borderColor
{
    UIImage *scaledImage = [self pp_imageScaledAspectToFillSize:newSize];  // 缩放图片
    UIGraphicsBeginImageContextWithOptions(scaledImage.size, NO, 0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect rect = CGRectMake(0, 0, scaledImage.size.width, scaledImage.size.height);
    CGContextScaleCTM(context, 1, -1);
    CGContextTranslateCTM(context, 0, -rect.size.height);
    
    CGFloat minSize = MIN(scaledImage.size.width, scaledImage.size.height);
    if (borderWidth < minSize / 2) {
        UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectInset(rect, borderWidth, borderWidth) byRoundingCorners:corners cornerRadii:CGSizeMake(radius, borderWidth)];
        CGContextSaveGState(context);
        [path addClip];
        CGContextDrawImage(context, rect, scaledImage.CGImage);
        CGContextRestoreGState(context);
    }
    
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    image = [image pp_imageByRoundBorderedColor:borderColor borderWidth:borderWidth];   	// 加上边框
    UIGraphicsEndImageContext();
    return image;
}
// 图片加边框
- (UIImage *)pp_imageByRoundBorderedColor:(UIColor *)borderColor
                              borderWidth:(CGFloat)borderWidth
{
    if (self.size.height != self.size.width) {
        return self;
    }
    
    if (!borderColor || borderWidth > self.size.width / 2 || borderWidth < 0) {
        return self;
    }
    
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0);
    [self drawAtPoint:CGPointZero];
    CGRect rect = CGRectMake(0, 0, self.size.width, self.size.height);
    CGFloat strokeInset = borderWidth / 2;
    CGRect strokeRect = CGRectInset(rect, strokeInset, strokeInset);
    CGFloat radius = self.size.width / 2;
    UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:strokeRect byRoundingCorners:UIRectCornerAllCorners cornerRadii:CGSizeMake(radius, borderWidth)];
    path.lineWidth = borderWidth;
    [borderColor setStroke];
    [path stroke];
    UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return result;
}

- (void)setAvatarImage:(UIImage *)avatarImage
{
    if (_avatarImage != avatarImage) {
        _avatarImage = avatarImage;
        
        _isNeedTransform = YES;      // 需要刷新的标识
        [self setNeedsLayout];
    }
}
- (void)setBorderHidden:(BOOL)borderHidden
{
    if (_borderHidden != borderHidden) {
        _borderHidden = borderHidden;
        
        _isNeedTransform = YES;		// 需要刷新的标识
        [self setNeedsLayout];
    }
}
+ (NSOperationQueue *)sharedTransformQueue
{
    static NSOperationQueue *transformQueue;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        transformQueue = [[NSOperationQueue alloc] init];
        transformQueue.name = @"io.github.vernonvan.PPRoundedAvatar.sharedOperationQueue";
        transformQueue.maxConcurrentOperationCount = 20;
    });
    return transformQueue;
}
- (void)layoutSubviews
{
    [super layoutSubviews];
    
    if (!self.avatarImage && !self.imageBackgroundColor) {
        return;
    }
    
    if (self.bounds.size.width <= 0 || self.bounds.size.height <= 0) {
        return;
    }
    if (_isNeedTransform || !CGSizeEqualToSize(self.bounds.size, self.imageView.image.size)) {
        [self transformImage];
    }
}
- (void)transformImage
{
    UIImage *startImage = self.avatarImage;
    
    NSBlockOperation *transformOperation = [[NSBlockOperation alloc] init];
    __weak NSBlockOperation *weakTransformOperation = transformOperation;
    [transformOperation addExecutionBlock:^{
        NSBlockOperation *strongTransformOperation = weakTransformOperation;
        
        if ([strongTransformOperation isCancelled]) {
            return;
        }
        
        UIImage *transformedImage = nil;
        if (self.avatarImage) {
            transformedImage = [self.avatarImage pp_imageByRoundCornerRadius:self.bounds.size.width scaleSize:self.bounds.size];
        } else if (self.imageBackgroundColor) {
            transformedImage = [UIImage pp_roundImageWithColor:self.imageBackgroundColor radius:self.bounds.size.width / 2];
        }
        
        if (!self.borderHidden) {
            transformedImage = [transformedImage pp_imageByRoundBorderedColor:self.borderColor borderWidth:self.borderWidth];
        }
        
        dispatch_async(dispatch_get_main_queue(), ^{
            if ([strongTransformOperation isCancelled]) {
                return;
            }
            if (self.avatarImage == startImage) {  // 1
                _isNeedTransform = NO;
                [self setImage:transformedImage forState:UIControlStateNormal];
            }
        });
    }];
    
    [[self.class sharedTransformQueue] addOperation:transformOperation];
}

PPRoundedAvatar *avatar = [[PPRoundedAvatar alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
avatar.avatarImage = [UIImage imageNamed:@"example.png"];       // 头像图片
avatar.borderWidth = 1.0;                                       // 边框宽度
avatar.borderColor = UIColor.blackColor;                        // 边框颜色
avatar.borderHidden = NO;                                       // 显示边框
avatar.imageBackgroundColor = UIColor.grayColor;                // 背景颜色
[self.view addSubview:avatar];