带颜色渐变的UIBezierPath

Question

我有一个关于UIBezierPath的问题.

例如,我有这条路:

现在我想要一个从白色到红色的颜色渐变.从左到右.

这是我的代码:

UIBezierPath *bezierPath;
bezierPath = [UIBezierPath bezierPathWithArcCenter:_center radius:_radius startAngle:((4 * angle)) endAngle:(((20) * angle)) clockwise:YES];
[bezierPath addLineToPoint:_center];
[bezierPath closePath];
UIColor *color = [UIColor colorWithHue:0/sectors saturation:1. brightness:1. alpha:1];
[color setFill];
[color setStroke];
[bezierPath fill];
[bezierPath stroke];

谁能帮我？

编辑1:

我有这个色轮:

    UIBezierPath *bezierPath;

for ( int i = 0; i < 360; i++) {
    bezierPath = [UIBezierPath bezierPathWithArcCenter:_center radius:_radius startAngle:((i * angle)) endAngle:(((i + 1) * angle)) clockwise:YES];

    [bezierPath addLineToPoint:_center];
    [bezierPath closePath];
    UIColor *color = [UIColor colorWithHue:i/sectors saturation:1. brightness:1. alpha:1];
    [color setFill];
    [color setStroke];
    [bezierPath fill];
    [bezierPath stroke];
}

但我想要这个:(用白色渐变色)

Answer 1

你可以尝试一下:)

- (void)drawRect:(CGRect)rect
{
    CGFloat arcStep = (M_PI *2) / 360; // M_PI*2 is equivalent of full cirle
    BOOL clocklwise = NO;
    CGFloat x = CGRectGetWidth(rect) / 2; // circle's center
    CGFloat y = CGRectGetHeight(rect) / 2; // circle's center
    CGFloat radius = MIN(x, y) / 2;
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    // draw colorful circle
    CGContextSetLineWidth(ctx, radius*2);
    for (CGFloat i = 0; i < 360; i+=1)
    {
        UIColor* c = [UIColor colorWithHue:i/360 saturation:1. brightness:1. alpha:1];

        CGContextSetStrokeColorWithColor(ctx, c.CGColor);

        CGFloat startAngle = i * arcStep;
        CGFloat endAngle = startAngle + arcStep + 0.02;

        CGContextAddArc(ctx, x, y, radius, startAngle, endAngle, clocklwise);
        CGContextStrokePath(ctx);
    }
    // drawing circles then, you might want few of them - smaller radius and less alpha with each step
    UIColor* c = [[UIColor whiteColor] colorWithAlphaComponent: 0.03];
    for (CGFloat fillRadius = radius/2; fillRadius > 0; fillRadius -= 1.f)
    {
        CGContextSetLineWidth(ctx, fillRadius*2);
        CGContextSetStrokeColorWithColor(ctx, c.CGColor);
        CGContextAddArc(ctx, x, y, fillRadius, 0, M_PI * 2, clocklwise);
        CGContextStrokePath(ctx);
    }
}