获取CGPoint的边缘/外部坐标

我有一个功能，用户可以绘制/着色图像的特定区域，然后将绘制区域作为裁剪结果。获取CGPoint的边缘/外部坐标

enter image description here

目前我存储阵列内的拉伸坐标，并且在该过程结束时，我使用UIBezierPath和CGContextClipToMask裁剪图像。问题是我只需要从我存储在数组中的绘制坐标的外部坐标。有什么办法来过滤CGPoints只获得外部坐标？

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { 

    // add the first coordinate 
    [points addObject:[NSValue valueWithCGPoint:lastPoint]]; 
} 

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { 

    // add more coordinates as finger moves 
    [points addObject:[NSValue valueWithCGPoint:currentPoint]]; 

} 

- (void) crop { 


    CGRect rect = CGRectZero; 
    rect.size = self.mainImage.image.size; 

    UIGraphicsBeginImageContextWithOptions(rect.size, YES, 0.0); 

    { 

     [[UIColor blackColor] setFill]; 
     UIRectFill(rect); 
     [[UIColor whiteColor] setFill]; 

     UIBezierPath * beziPath = [UIBezierPath bezierPath]; 

     NSValue * firstValue = [points objectAtIndex:0]; 
     CGPoint firstPoint = firstValue.CGPointValue; 
     [beziPath moveToPoint:[ARCroppingViewController 
         convertCGPoint:firstPoint fromRect1:self.mainImage.frame.size 
         toRect2:self.mainImage.image.size]]; 

     for (uint i = 1; i < points.count; i++) { 


      NSValue * value = [points objectAtIndex:i]; 
      CGPoint point = value.CGPointValue; 
      NSLog(@"point: %@", NSStringFromCGPoint(point)); 
      [beziPath addLineToPoint:[ARCroppingViewController 
          convertCGPoint:point fromRect1:self.mainImage.frame.size 
          toRect2:self.mainImage.image.size]]; 

      } 

    [beziPath closePath]; 
    [beziPath fill]; 


     } 


    UIImage *mask = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 

    UIGraphicsBeginImageContextWithOptions(rect.size, NO, 0.0); 
    { 

     CGContextClipToMask(UIGraphicsGetCurrentContext(), rect, mask.CGImage); 
     [self.mainImage.image drawAtPoint:CGPointZero]; 

    } 

    UIImage *maskedImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 
    NSLog(@"mask image: %@", NSStringFromCGSize(maskedImage.size)); 
    self.mainImage.image = maskedImage; 

}

来源

2013-05-06 ariauakbar

为了获得边缘，我会保存已经处于保存阶段的极端值（将点添加到数组中）。所以保持最高和最低的x和y值。认为它也比滤波阵列:)

编辑

int xMin, xMax, yMin, yMax; 
-(void)resetValues 
{ 
    xMax = yMax = 0; 

    xMin = yMin = self.mainImage.image.size.width; 
} 

- (void)checkForExtremes:(CGPoint)point 
{ 
    // Have my IDE not here for checking the MIN() and MAX(), so using this way :P 
    lastPoint.x > xMax ? xMax = lastPoint.x : nil; 
    lastPoint.x < xMin ? xMin = lastPoint.x : nil; 
    lastPoint.y > yMax ? yMax = lastPoint.y : nil; 
    lastPoint.y < yMin ? yMin = lastPoint.y : nil; 
} 

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { 

    // add the first coordinate 
    [points addObject:[NSValue valueWithCGPoint:lastPoint]]; 

    [self checkForExtremes:lastPoint]; 
} 

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { 

    // add more coordinates as finger moves 
    [points addObject:[NSValue valueWithCGPoint:currentPoint]]; 
    [self checkForExtremes:currentPoint]; 
}

BTW容易，结果是那么

cut Image

来源

2013-05-06 14:45:15 geo

如何获得极值？ – ariauakbar 2013-05-06 15:14:41

检查我的编辑:) – geo 2013-05-06 16:05:46

谢谢，我会试试你的答案。但是我需要一个精确的圆形裁剪结果（与绘图路径相同） – ariauakbar 2013-05-06 17:11:34

就遍历所有的点（你现在的样子）但检查每个点并存储x和y值的最大值和最小值。然后在循环结束时，您可以在（现在正方形）所选区域的角落获得4个点。

CGFloat minX, maxX, minY, maxY; 

for (... { 
    minX = MIN(minX, point.x); 
    maxX = ... 
} 

CGPoint topLeft = CGPointMake(minX, minY); 
CGPoint topRight = ...

你也可以在用户追踪形状（你也可以修改贝塞尔路径则太）进行计算。

来源

2013-05-06 14:47:42 Wain

获取CGPoint的边缘/外部坐标

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