iOS简单的画线（UIImageVIew方式）

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
{
    UIImageView *mImageView;
}

@end

　　

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	mImageView = [[UIImageView alloc] initWithFrame:self.view.frame];
    mImageView.backgroundColor = [UIColor grayColor];
    [self.view addSubview:mImageView];
    UIGraphicsBeginImageContext(mImageView.frame.size);
    [mImageView.image drawInRect:CGRectMake(0, 0, mImageView.frame.size.width, mImageView.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 15);
    CGContextSetAllowsAntialiasing(UIGraphicsGetCurrentContext(), YES);
    CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), [[UIColor blueColor] CGColor]);
    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), 100, 100);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), 200, 200);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    mImageView.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

@end