IOS图片的原生（Graphics）详解及实例

#import "RootViewController.h"

@interface RootViewController ()

@end

@implementation RootViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
  self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
  if (self) {
    // Custom initialization
  }
  return self;
}

- (void)viewDidLoad
{
  [super viewDidLoad];
  // Do any additional setup after loading the view.
  
  //背景图
  [self addView];
  
}

#pragma -mark -functions
//背景图
-(void)addView
{
  UIImageView *imageView=[[UIImageView alloc]initWithFrame:CGRectMake(50, 100, 44, 44)];
  imageView.image=[self defaultImage];
  [self.view addSubview:imageView];
}
//图片原生
-(UIImage *)defaultImage {
  
  static UIImage *defaultImage = nil;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(20.f, 13.f), NO, 0.0f);
    
    [[UIColor blackColor] setFill];
    [[UIBezierPath bezierPathWithRect:CGRectMake(0, 0, 20, 1)] fill];
    [[UIBezierPath bezierPathWithRect:CGRectMake(0, 5, 20, 1)] fill];
    [[UIBezierPath bezierPathWithRect:CGRectMake(0, 10, 20, 1)] fill];
    
    [[UIColor whiteColor] setFill];
    [[UIBezierPath bezierPathWithRect:CGRectMake(0, 1, 20, 2)] fill];
    [[UIBezierPath bezierPathWithRect:CGRectMake(0, 6, 20, 2)] fill];
    [[UIBezierPath bezierPathWithRect:CGRectMake(0, 11, 20, 2)] fill];
    
    defaultImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
  });
  return defaultImage;
}

- (void)didReceiveMemoryWarning
{
  [super didReceiveMemoryWarning];
  // Dispose of any resources that can be recreated.
}