Quartz和Uikit坐标系：

UIImage *image = [UIImage imageNamed:@"lx_20180118102017.png"];

UIGraphicsBeginImageContext(image.size);

CGContextRef context = UIGraphicsGetCurrentContext();

CGContextDrawImage(context, CGRectMake(0, 0, image.size.width, image.size.height), [image CGImage]);

image = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

UIImageView *imageV = [[UIImageView alloc]initWithImage:image];

imageV.frame = self.view.bounds;

[self.view addSubview:imageV];

上下文中加入转换坐标系代码：

    CGContextRotateCTM(context, M_PI);

    CGContextScaleCTM(context, -1, 1);

    CGContextTranslateCTM(context, 0, -image.size.height);