1 #import "ViewController.h" 2 #import "SecondVC.h" 3  4  5 #define WIDTH [UIScreen mainScreen].bounds.size.width 6 #define HEIGHT [UIScreen mainScreen].bounds.size.height 7  8 @interface ViewController () 9 {10     UIImageView *_canvasView;//画布11     CGPoint _startPoint;//记录开始坐标12     13 }14 @end15 16 @implementation ViewController17 18 - (void)viewDidLoad {19     [super viewDidLoad];20     21     _canvasView = [[UIImageView alloc] initWithFrame:self.view.bounds];22     [self.view addSubview:_canvasView];23     24     UIButton *clearBtn = [UIButton buttonWithType:UIButtonTypeCustom];25     clearBtn.frame = CGRectMake(50, 20, 100, 30);26     [clearBtn addTarget:self action:@selector(clearBtnClick) forControlEvents:UIControlEventTouchUpInside];27     [clearBtn setTitle:@"清空" forState:UIControlStateNormal];28     clearBtn.backgroundColor = [UIColor orangeColor];29     [self.view addSubview:clearBtn];30     31     UIButton *cutPicBtn = [UIButton buttonWithType:UIButtonTypeCustom];32     cutPicBtn.frame = CGRectMake(250, 20, 100, 30);33     [cutPicBtn addTarget:self action:@selector(cutPicBtnClick) forControlEvents:UIControlEventTouchUpInside];34     [cutPicBtn setTitle:@"截图" forState:UIControlStateNormal];35     cutPicBtn.backgroundColor = [UIColor orangeColor];36     [self.view addSubview:cutPicBtn];37     38 }39 40 41 - (void)touchesBegan:(NSSet
     
       *)touches withEvent:(UIEvent *)event42 {43     _startPoint = [[touches anyObject] locationInView:_canvasView];44 45 }46 47 - (void)touchesMoved:(NSSet
      
        *)touches withEvent:(UIEvent *)event48 {49     CGPoint movePoint = [[touches anyObject] locationInView:_canvasView];50 51 //    移动的点有很多，52     @autoreleasepool {53         UIGraphicsBeginImageContext(CGSizeMake(WIDTH, HEIGHT));//开始一个图片的绘图54         55         [_canvasView drawRect:_canvasView.frame];//绘制原来已经存在的线条56         57         CGContextRef context = UIGraphicsGetCurrentContext();//绘图缓存区，当前的是一张图片58         CGContextSetLineWidth(context, 5);59         CGContextSetRGBStrokeColor(context, 1, 0, 0, 1);60         CGContextSetLineCap(context, kCGLineCapRound);//边帽61         CGContextSetLineJoin(context, kCGLineJoinRound);//缝合62         63         CGContextMoveToPoint(context, _startPoint.x, _startPoint.y);64         CGContextAddLineToPoint(context, movePoint.x, movePoint.y);65         CGContextStrokePath(context);66         _canvasView.image = UIGraphicsGetImageFromCurrentImageContext();//获取当前图片绘制区域内的图片67         68         UIGraphicsEndImageContext();//关闭图片绘制69     }70     71     _startPoint = movePoint;72 }73 74 75 #pragma mark - 清除按钮76 - (void)clearBtnClick77 {78     79     _canvasView.image = nil;//这并不是一个好办法。80     81 }82 83 #pragma mark - 剪切按钮84 - (void)cutPicBtnClick85 {86     UIGraphicsBeginImageContext(CGSizeMake(WIDTH, HEIGHT));//开始一个图片的绘图87 //    在屏幕加载之后截图88     [self.view drawViewHierarchyInRect:self.view.frame afterScreenUpdates:YES];89     90     UIImage *image = UIGraphicsGetImageFromCurrentImageContext();//获取当前图片绘制区域内的图片91     92     UIGraphicsEndImageContext();93     94     SecondVC *vc = [[SecondVC alloc] init];95     vc.image = image;96     [self presentViewController:vc animated:YES completion:nil];97 }