一、UIImage裁圆

+ (instancetype)circleImageWithName:(NSString *)name borderWidth:(CGFloat)borderWidth borderColor:(UIColor *)borderColor
{
    // 1.加载原图
    UIImage *oldImage = [UIImage imageNamed:name];
    // 2.开启上下文
    CGFloat imageW = oldImage.size.width + 2 * borderWidth;
    CGFloat imageH = oldImage.size.height + 2 * borderWidth;
    CGSize imageSize = CGSizeMake(imageW, imageH);
    UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0.0);
    // 3.取得当前的上下文
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    // 4.画边框(大圆)
    [borderColor set];
    CGFloat bigRadius = imageW * 0.5; // 大圆半径
    CGFloat centerX = bigRadius; // 圆心
    CGFloat centerY = bigRadius;
    CGContextAddArc(ctx, centerX, centerY, bigRadius, 0, M_PI * 2, 0);
    CGContextFillPath(ctx); // 画圆
    // 5.小圆
    CGFloat smallRadius = bigRadius - borderWidth;
    CGContextAddArc(ctx, centerX, centerY, smallRadius, 0, M_PI * 2, 0);
    // 裁剪(后面画的东西才会受裁剪的影响)
    CGContextClip(ctx);
    // 6.画图
    [oldImage drawInRect:CGRectMake(borderWidth, borderWidth, oldImage.size.width, oldImage.size.height)];
    // 7.取图
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    // 8.结束上下文
    UIGraphicsEndImageContext();
    return newImage;
}

二、UIImageView裁圆

//只是显示圆角
UIImageView *imageView = nil;
imageView.layer.cornerRadius = 10;
imageView.layer.masksToBounds = YES;
//需要裁剪成圆角图片，这个步骤比较多
UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, 0, [UIScreen mainScreen].scale);
CGContextRef context = UIGraphicsGetCurrentContext();
[imageView.layer renderInContext:context];
//这个图片就是裁剪的圆角图片
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
CGContextRelease(context);

有的时候image本身不是正方形的这个时候可以裁剪成正方形

三、UIImage裁剪成正方形

/**
 *  剪切图片为正方形
 *
 *  @param image   原始图片比如size大小为(400x200)pixels
 *  @param newSize 正方形的size比如400pixels
 *
 *  @return 返回正方形图片(400x400)pixels
 */
+ (UIImage *)squareImageFromImage:(UIImage *)image scaledToSize:(CGFloat)newSize {
    CGAffineTransform scaleTransform;
    CGPoint origin;
    
    if (image.size.width > image.size.height) {
        //image原始高度为200，缩放image的高度为400pixels，所以缩放比率为2
        CGFloat scaleRatio = newSize / image.size.height;
        scaleTransform = CGAffineTransformMakeScale(scaleRatio, scaleRatio);
        //设置绘制原始图片的画笔坐标为CGPoint(-100, 0)pixels
        origin = CGPointMake(-(image.size.width - image.size.height) / 2.0f, 0);
    } else {
        CGFloat scaleRatio = newSize / image.size.width;
        scaleTransform = CGAffineTransformMakeScale(scaleRatio, scaleRatio);
        
        origin = CGPointMake(0, -(image.size.height - image.size.width) / 2.0f);
    }
    
    CGSize size = CGSizeMake(newSize, newSize);
    //创建画板为(400x400)pixels
    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
        UIGraphicsBeginImageContextWithOptions(size, YES, 0);
    } else {
        UIGraphicsBeginImageContext(size);
    }
    
    CGContextRef context = UIGraphicsGetCurrentContext();
    //将image原始图片(400x200)pixels缩放为(800x400)pixels
    CGContextConcatCTM(context, scaleTransform);
    //origin也会从原始(-100, 0)缩放到(-200, 0)
    [image drawAtPoint:origin];
    //获取缩放后剪切的image图片
    image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

四、图片旋转(静态)

- (UIImage *)image:(UIImage *)image rotation:(UIImageOrientation)orientation{
    long double rotate = 0.0;
    CGRect rect;
    float translateX = 0;
    float translateY = 0;
    float scaleX = 1.0;
    float scaleY = 1.0;
    
    switch (orientation) {
        case UIImageOrientationLeft:
            rotate = M_PI_2;
            rect = CGRectMake(0, 0, image.size.height, image.size.width);
            translateX = 0;
            translateY = -rect.size.width;
            scaleY = rect.size.width/rect.size.height;
            scaleX = rect.size.height/rect.size.width;
            break;
        case UIImageOrientationRight:
            rotate = 33 * M_PI_2;
            rect = CGRectMake(0, 0, image.size.height, image.size.width);
            translateX = -rect.size.height;
            translateY = 0;
            scaleY = rect.size.width/rect.size.height;
            scaleX = rect.size.height/rect.size.width;
            break;
        case UIImageOrientationDown:
            rotate = M_PI;
            rect = CGRectMake(0, 0, image.size.width, image.size.height);
            translateX = -rect.size.width;
            translateY = -rect.size.height;
            break;
        default:
            rotate = 0.0;
            rect = CGRectMake(0, 0, image.size.width, image.size.height);
            translateX = 0;
            translateY = 0;
            break;
    }
    
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    //做CTM变换
    CGContextTranslateCTM(context, 0.0, rect.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextRotateCTM(context, rotate);
    CGContextTranslateCTM(context, translateX, translateY);
    
    CGContextScaleCTM(context, scaleX, scaleY);
    //绘制图片
    CGContextDrawImage(context, CGRectMake(0, 0, rect.size.width, rect.size.height), image.CGImage);
    UIImage *newPic = UIGraphicsGetImageFromCurrentImageContext();
    return newPic;
}

五、图片旋转动画(UIImageView)

//transform.rotation.x绕x轴旋转、transform.rotation.y绕y轴旋转、transform.rotation.z绕z轴旋转
CABasicAnimation *rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.x"];
    rotationAnimation.toValue = [NSNumber numberWithFloat:M_PI * 2.0];
    rotationAnimation.duration = 1.0;
    rotationAnimation.cumulative = YES;
    rotationAnimation.repeatCount =ULLONG_MAX;