图片处理相关

Contents

1. 1. UIImage相关扩展
   1. 1.1. 1.裁剪成圆形（头像使用较多）
   2. 1.2. 2.在某些地方加载出来的图片是经过系统渲染过的，该方法是告诉系统不需要渲染加载的图片
   3. 1.3. 3.返回一张抗锯齿图片(本质：在图片周边加一个边框为1的透明像素)

UIImage相关扩展

1.裁剪成圆形（头像使用较多）

- (instancetype)xmg_circleImage
{
    // 1.开启图形上下文
    // 比例因素:当前点与像素比例
    UIGraphicsBeginImageContextWithOptions(self.size, NO, 0);
    // 2.描述裁剪区域
    UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, self.size.width, self.size.height)];
    // 3.设置裁剪区域;
    [path addClip];
    // 4.画图片
    [self drawAtPoint:CGPointZero];
    // 5.取出图片
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    // 6.关闭上下文
    UIGraphicsEndImageContext();
    
    return image;
}

+ (instancetype)xmg_circleImageNamed:(NSString *)name
{
    return [[self imageNamed:name] xmg_circleImage];
}
@end

2.在某些地方加载出来的图片是经过系统渲染过的，该方法是告诉系统不需要渲染加载的图片

+ (instancetype)xmg_circleImageNamed:(NSString *)name
{
    return [[self imageNamed:name] xmg_circleImage];
}

3.返回一张抗锯齿图片(本质：在图片周边加一个边框为1的透明像素)

- (UIImage *)imageAntialias
{
    CGFloat border = 1.0f;
    CGRect rect = CGRectMake(border, border, self.size.width-2*border, self.size.height-2*border);
    
    UIImage *img = nil;
    
    UIGraphicsBeginImageContext(CGSizeMake(rect.size.width,rect.size.height));
    [self drawInRect:CGRectMake(-1, -1, self.size.width, self.size.height)];
    img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    UIGraphicsBeginImageContext(self.size);
    [img drawInRect:rect];
    UIImage* antiImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    return antiImage;
}