根据两点坐标及父视图绘制直线

    UIImageView *imageView=[[UIImageView alloc] initWithFrame:self.view.frame];

    [self.view addSubview:imageView];

   

    UIGraphicsBeginImageContext(imageView.frame.size);

    [imageView.image drawInRect:CGRectMake(0, 0, imageView.frame.size.width, imageView.frame.size.height)];

    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapButt);  //边缘样式

    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 1.0);  //线宽

    CGContextSetAllowsAntialiasing(UIGraphicsGetCurrentContext(), YES);

    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);  //颜色

    CGContextBeginPath(UIGraphicsGetCurrentContext());

    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), 100, 100);  //起点坐标

    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), 200, 100);   //终点坐标

    CGContextStrokePath(UIGraphicsGetCurrentContext());

    imageView.image=UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();