Question

我正在使用

绘制线条

CGMutablePathRef path = CGPathCreateMutable();

for (int i = 0; i < [_points count]; i++)
{
    CGPoint pt = [[_points objectAtIndex:i] CGPointValue];
    if (i == 0)
    {
        CGPathMoveToPoint(path, NULL, pt.x+1, pt.y+1);
    }
    else
    {
        CGPathAddLineToPoint(path, NULL, pt.x+1, pt.y+1);
    }
}

CGContextSetLineWidth(context, 1.0f);
CGContextSetStrokeColorWithColor(context, curveColor.CGColor);
CGContextAddPath(context, path);
CGContextStrokePath(context);
CGPathRelease(path);

我可以将线条向一个方向扩展。但我想在一定程度上向两个方向（上行和下行）延伸线。如何在两个方向延长线？

Answer 1

扩展一端：

[_points insertObject:newStartPoint atIndex:0];

和另一个：

[_points addObject:newEndPoint];

Answer 2

终于在@Wain评论的帮助下得到了答案，

- (NSArray *)lineDrawingPoints:(CGFloat)slope pointX1:(CGFloat)ptX1 pointY1:(CGFloat)ptY1 maxValX:(CGFloat)biggestNumberX maxValY:(CGFloat)biggestNumberY {

    NSMutableArray *infiniteLinePoints = [NSMutableArray array];
    float y;

    for(int x = -biggestNumberX ; x <= biggestNumberX ; x++ ){
        y = slope * (x - ptX1)+ptY1;
        if(y >= -biggestNumberY && y <= biggestNumberY )
           [infiniteLinePoints addObject:[NSValue valueWithCGPoint:CGPointMake(x, y)]];
    }

    return infiniteLinePoints;
}

谢谢Wain。

如何在两个方向上扩展使用CGMutablePathRef绘制的线？

2 个答案: