绘制抗锯齿线

Question

我正在屏幕上画一条线，其中包括对角线，而对角线又是这样绘制的：

注意它看起来一点也不平滑。我已经阅读了几篇关于此的文章，似乎 this 看起来更接近我遇到的问题，但该解决方案对我不起作用。

这是我设置图层的方法：

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Instantiate the navigation line view
    CGRect navLineFrame = CGRectMake(0.0f, 120.0f, self.view.frame.size.width, 15.0f);
    self.navigationLineView = [[HyNavigationLineView alloc] initWithFrame:navLineFrame];

    // Make it's background transparent
    self.navigationLineView.backgroundColor = [UIColor colorWithWhite:0.0f alpha:0.0f];
    self.navigationLineView.opaque = NO;

    HyNavigationLineLayer * layer = [[HyNavigationLineLayer alloc] init];
    layer.shouldRasterize = YES;
    layer.rasterizationScale = [UIScreen mainScreen].scale;
    layer.contentsScale = [[UIScreen mainScreen] scale];
    layer.needsDisplayOnBoundsChange = YES;

    [[self.navigationLineView layer] addSublayer:layer];
    [self.view addSubview:self.navigationLineView];
    [self.navigationLineView.layer setNeedsDisplay];
}

这是我在图层中的绘制方式：

- (void)drawInContext:(CGContextRef)ctx
{
    CGFloat bottomInset = 1.0f / [[UIScreen mainScreen] scale] * 2.0f;

    CGContextSetInterpolationQuality(ctx, kCGInterpolationHigh);
    CGContextSetStrokeColorWithColor(ctx, [UIColor whiteColor].CGColor);

    GLfloat padding = kHyNavigationLineViewPadding * 4.0f;
    GLfloat searchSpace = self.frame.size.width - padding - kHyNavigationLineViewPointerSize * 2.0f;
    GLfloat x = kHyNavigationLineViewPadding * 2.0f + searchSpace * self.offset;

    CGContextSetLineWidth(ctx, 2.0f);
    CGContextMoveToPoint(ctx, kHyNavigationLineViewPadding, 0.0f);
    CGContextAddLineToPoint(ctx, x, bottomInset);
    CGContextAddLineToPoint(ctx, x + kHyNavigationLineViewPointerSize, self.frame.size.height);
    CGContextAddLineToPoint(ctx, x + kHyNavigationLineViewPointerSize * 2.0f, bottomInset);
    CGContextAddLineToPoint(ctx, self.frame.size.width - kHyNavigationLineViewPadding, 0.0f);

    // Draw
    CGContextStrokePath(ctx);
}

关于如何解决这个问题的任何提示？

编辑：忘了提到我首先在图层中绘制的原因：我需要为使这条线动画的属性设置动画效果很好，所以在drawRect 中绘制不起作用。

Answer 1

你可以使用 UIBezierPath 代替使用quartz来渲染代码：

UIBezierPath* path = [UIBezierPath bezierPath];

[[UIColor whiteColor] setStroke];

GLfloat padding = kHyNavigationLineViewPadding * 4.0f;
GLfloat searchSpace = self.frame.size.width - padding - kHyNavigationLineViewPointerSize * 2.0f;
GLfloat x = kHyNavigationLineViewPadding * 2.0f + searchSpace * self.offset;

path.lineWidth = 2.0;
[path moveToPoint:CGPointMake(kHyNavigationLineViewPadding, 0)];
[path addLineToPoint:CGPointMake(x, bottomInset)];
[path addLineToPoint:CGPointMake(x + kHyNavigationLineViewPointerSize, self.frame.size.height)];
[path addLineToPoint:CGPointMake(x + kHyNavigationLineViewPointerSize * 2.0f, bottomInset)];
[path addLineToPoint:CGPointMake(self.frame.size.width - kHyNavigationLineViewPadding, 0.0f)];

[path stroke];