如何在任何线条周围绘制轮廓
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所以我有一条由n个点组成的任意曲线（请参见图1中的示例）
我想在这条线周围画一个轮廓（见图2），所以我需要计算周围多边形的点。
我从在线路上执行膨胀开始，但是这行不通-见图3
有关如何执行此操作的任何建议？
我怀疑要计算每个线段的法线，以用于平移下面的新线以及在其当前位置上方平移新线，然后将每条新线扩展到无穷大并将点定义为交点？
没有找到相关结果
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5 个回复
广躺椽
补蹲农界维
破弯
鞋扣蚊冈借
扇献隙
- (hOzPolygon2D *) convertToPolygonWithWidth:(double) polyWidth { double shift = polyWidth / 2.; NSMutableArray *tempEdgesRight = [[[NSMutableArray alloc] init] autorelease]; NSMutableArray *tempEdgesLeft = [[[NSMutableArray alloc] init] autorelease]; NSMutableArray *tempPolyPoints = [[[NSMutableArray alloc] init] autorelease]; // Move your points on the right by half the desired width // My edges are already computed in a NSArray* called edges, // but you can use pairs of vectors and adapt all this for (hOzEdge2D *edge in edges) { hOzVector2 v = hOzVector2([[edge pointB] x] - [[edge pointA] x], [[edge pointB] y] - [[edge pointA] y]); double mag = sqrt (v.x * v.x + v.y * v.y); v.x = v.x / mag; v.y = v.y / mag; double temp = v.x; v.x = v.y; v.y = -temp; hOzPoint2D *newPointA = [[hOzPoint2D alloc] init]; [newPointA setX:([[edge pointA] x] + v.x * shift)]; [newPointA setY:([[edge pointA] y] + v.y * shift)]; hOzPoint2D *newPointB = [[hOzPoint2D alloc] init]; [newPointB setX:([[edge pointB] x] + v.x * shift)]; [newPointB setY:([[edge pointB] y] + v.y * shift)]; [tempEdgesRight addObject:[hOzEdge2D edge2DWithPointA:newPointA pointB:newPointB]]; } // With the same polyline, move on the left for (int j = [edges count] - 1; j >= 0; j--) { hOzVector2 v = hOzVector2([[[edges objectAtIndex:j] pointB] x] - [[[edges objectAtIndex:j] pointA] x], [[[edges objectAtIndex:j] pointB] y] - [[[edges objectAtIndex:j] pointA] y]); double mag = sqrt (v.x * v.x + v.y * v.y); v.x = v.x / mag; v.y = v.y / mag; double temp = v.x; v.x = v.y; v.y = -temp; hOzPoint2D *newPointA = [[hOzPoint2D alloc] init]; [newPointA setX:([[[edges objectAtIndex:j] pointB] x] - v.x * shift)]; [newPointA setY:([[[edges objectAtIndex:j] pointB] y] - v.y * shift)]; hOzPoint2D *newPointB = [[hOzPoint2D alloc] init]; [newPointB setX:([[[edges objectAtIndex:j] pointA] x] - v.x * shift)]; [newPointB setY:([[[edges objectAtIndex:j] pointA] y] - v.y * shift)]; [tempEdgesLeft addObject:[hOzEdge2D edge2DWithPointA:newPointA pointB:newPointB]]; } // Add the static points and the intersection points to a points array that will define your polygon [tempPolyPoints addObject:[[tempEdgesRight objectAtIndex:0] pointA]]; // The first point of the right array for (int k = 0; k < [tempEdgesRight count] - 1; k++) { // For this function, see the link below in the answer hOzPoint2D *inter = [[tempEdgesRight objectAtIndex:k] getIntersectionWithStraight:[tempEdgesRight objectAtIndex:k+1]]; if (inter == nil) { // if the edges are parallel, we insert a known point [tempPolyPoints addObject:[[tempEdgesRight objectAtIndex:k] pointB]]; } else { [tempPolyPoints addObject:inter]; } } [tempPolyPoints addObject:[[tempEdgesRight lastObject] pointB]]; // The last point of the right array [tempPolyPoints addObject:[[tempEdgesLeft objectAtIndex:0] pointA]]; // Then the left array, same thing for (int k = 0; k < [tempEdgesLeft count] - 1; k++) { hOzPoint2D *inter = [[tempEdgesLeft objectAtIndex:k] getIntersectionWithStraight:[tempEdgesLeft objectAtIndex:k+1]]; if (inter == nil) { [tempPolyPoints addObject:[[tempEdgesLeft objectAtIndex:k] pointB]]; } else { [tempPolyPoints addObject:inter]; } } [tempPolyPoints addObject:[[tempEdgesLeft lastObject] pointB]]; // Create your polygon with this new ordered points array. hOzPolygon2D *poly = [hOzPolygon2D polygon2DWithArrayOfPoints:tempPolyPoints]; return poly; }