IOS图片的原生（Graphics）详解及实例

#import <UIKit/UIKit.h>@interface RootViewController : UIViewController@end 

#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.}