Quartz 2D 手势截屏绘制

1、绘制手势截屏

• 具体实现代码见 GitHub 源码 QExtension

• QTouchClipView.h

  @interface QTouchClipView : UIView
      
  /**
   *  创建手势截屏视图控件，获取截屏结果
   *
   *  @param view     截取图片的视图控件
   *  @param result   手势截屏结果
   *
   *  @return 手势截屏视图控件
   */
  + (instancetype)q_touchClipViewWithView:(UIView *)view
                               clipResult:(void (^)(UIImage * _Nullable image))result;
      
  @end

• QTouchClipView.m

  @interface QTouchClipView ()
      
  /// 截取图片的视图控件
  @property (nonatomic, strong) UIView *baseView;
      
  /// 滑动手势结果
  @property (nonatomic, copy) void (^resultBlock)(UIImage * _Nullable);
      
  /// 触摸开始结束点
  @property (nonatomic, assign) CGPoint startP;
  @property (nonatomic, assign) CGPoint endP;
      
  @end
      
  @implementation QTouchClipView
      
  /// 创建手势截屏视图控件，获取截屏结果
  + (instancetype)q_touchClipViewWithView:(UIView *)baseView
                               clipResult:(void (^)(UIImage * _Nullable image))result {
      
      QTouchClipView *clipView = [[self alloc] initWithFrame:baseView.frame];
      
      clipView.baseView = baseView;
      clipView.resultBlock = result;
   
      return clipView;
  }
      
  /// 初始化
  - (instancetype)initWithFrame:(CGRect)frame {
      
      if (self = [super initWithFrame:frame]) {
          self.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.5];
      }
      return self;
  }
      
  /// 触摸开始
  - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {
      
      // 获取触摸起始点位置
      CGPoint startPoint = [touches.anyObject locationInView:self];
      self.startP = startPoint;
  }
      
  /// 触摸移动
  - (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {
      
      // 获取触摸点位置
      CGPoint touchPoint = [touches.anyObject locationInView:self];
      self.endP = touchPoint;
      
      // 刷新视图
      [self setNeedsDisplay];
  }
      
  /// 触摸结束
  - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(nullable UIEvent *)event {
      
      // 截取屏幕图片
      UIGraphicsBeginImageContextWithOptions(self.baseView.bounds.size, NO, 0);
      
      CGContextRef ctx = UIGraphicsGetCurrentContext();
      [self.baseView.layer renderInContext:ctx];
      
      UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
      
      UIGraphicsEndImageContext();
      
      // 切割图片
      CGFloat x = self.startP.x;
      CGFloat y = self.startP.y;
      CGFloat w = self.endP.x - x;
      CGFloat h = self.endP.y - y;
      
      CGRect cutRect = CGRectMake(x * 2, y * 2, w * 2, h * 2);
      
      CGImageRef cgImage = CGImageCreateWithImageInRect(image.CGImage, cutRect);
      UIImage *newImage = [[UIImage alloc] initWithCGImage:cgImage];
      CGImageRelease(cgImage);
      
      // 返回截取结果
      if (self.resultBlock) {
          self.resultBlock(newImage);
      }
      
      // 移除截取视图控件
      [self removeFromSuperview];
      self.startP = CGPointZero;
      self.endP = CGPointZero;
      
      // 刷新视图
      [self setNeedsDisplay];
  }
      
  /// 触摸取消
  - (void)touchesCancelled:(NSSet *)touches withEvent:(nullable UIEvent *)event {
      [self touchesEnded:touches withEvent:event];
  }
      
  /// 绘制触摸区域
  - (void)drawRect:(CGRect)rect {
      
      CGFloat x = self.startP.x;
      CGFloat y = self.startP.y;
      CGFloat w = self.endP.x - x;
      CGFloat h = self.endP.y - y;
      
      CGRect clipRect = CGRectMake(x, y, w, h);
      
      UIBezierPath *path = [UIBezierPath bezierPathWithRect:clipRect];
      [[[UIColor whiteColor] colorWithAlphaComponent:0.2] setFill];
      [path fill];
  }
      
  @end

• ViewController.m

  // 创建手势截屏视图
  QTouchClipView *touchClipView = [QTouchClipView q_touchClipViewWithView:self.imageView
                                                               clipResult:^(UIImage * _Nullable image) {
      
      // 获取处理截屏结果
      if (image) {
          UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
      }
  }];
      
  // 添加手势截屏视图
  [self.view addSubview:touchClipView];

• 效果