圆形 CAGradientLayer 蒙版 - iOS

Posted 2023-02-23

【中文标题】圆形 CAGradientLayer 蒙版 - iOS

【英文标题】：Circular CAGradientLayer Mask - iOS

【发布时间】：2014-05-06 06:45:04

【问题描述】：

我在我的图片上使用CAGradientLayer。我使用此代码来执行此操作：

UIImage *image = [UIImage imageNamed:@"perfect.jpg"];

[testImage setImage:image];

CAGradientLayer *myLayer = [CAGradientLayer layer];

myLayer.anchorPoint = CGPointZero;

//starts in bottom left
myLayer.startPoint = CGPointMake(1.0f,1.0f);

//ends in top right
myLayer.endPoint = CGPointMake(1.0f, 0.0f);

UIColor *outerColor = [UIColor colorWithWhite:1.0 alpha:0.0];
UIColor *innerColor = [UIColor colorWithWhite:1.0 alpha:1.0];

//an array of colors that dictatates the gradient(s)
myLayer.colors = @[(id)outerColor.CGColor, (id)outerColor.CGColor, (id)innerColor.CGColor, (id)innerColor.CGColor];

//these are percentage points along the line defined by our startPoint and endPoint and correspond to our colors array. The gradient will shift between the colors between these percentage points.
myLayer.locations = @[@0.0, @0.15, @0.5, @1.0f];

myLayer.bounds = CGRectMake(0, 0, CGRectGetWidth(testImage.bounds), CGRectGetHeight(testImage.bounds));

testImage.layer.mask = myLayer;

[self.view addSubview:testImage];

但我想要的是径向渐变或圆形渐变效果。我只在一侧得到渐变。如何实现圆形渐变层？谢谢。

【问题讨论】：

试试这个...它会帮助你。 ***.com/questions/8125623/…

【参考方案1】：

如果你想要一个圆形渐变层，你必须继承并覆盖- (void)drawInContext:(CGContextRef)ctx 方法。因为代码非常简单，对于径向渐变应该看起来像这样：

        CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
        NSArray* colors = @[(id)[UIColor whiteColor].CGColor, (id)[UIColor blackColor].CGColor];
        CGFloat locations[] = .25, .75;
        CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef)colors, locations);
        CGPoint center = (CGPoint)self.bounds.size.width / 2, self.bounds.size.height  / 2;
        CGContextDrawRadialGradient(ctx, gradient, center, 20, center, 40, kCGGradientDrawsAfterEndLocation);

        CGGradientRelease(gradient);
        CGColorSpaceRelease(colorSpace);

请注意，我现在无法测试代码，但应该没问题。如果你想要一个像这样的角度渐变而不是径向渐变：

你很不幸，因为 Objective c 无法直接实现它。要做到这一点，您可以循环遍历所需颜色之间的线性插值并直接绘制它们（实现起来并不难，但性能较差）或使用图像作为蒙版。

【讨论】：

您是子类化了 CLayer 还是渐变层？我无法执行图像中的渐变。

请仔细阅读：如果你想要一个像这样的角度渐变而不是径向渐变：[image_here] 你很不幸，因为 Objective c 无法直接制作它。为此，您可以循环遍历所需颜色之间的线性插值并直接绘制它们（实现起来并不难，但性能较差）或使用图像作为蒙版。

我所做的是：我创建了 2 个渐变框来模拟这种效果（一个在左侧，一个在右侧）。它并不完美，但有效。也许我应该像你说的那样尝试图像蒙版:)

【参考方案2】：

这是生成所附图像所示输出的代码：

CAGradientLayer *gradientLayer = [CAGradientLayer layer];
                        gradientLayer.frame = self.clockView.bounds;
                        [self.clockView.layer addSublayer:gradientLayer];
                        // TO-DO:
                        // add durations
                        gradientLayer.colors = @[(__bridge id)[UIColor colorWithRed:1.0/255.0 green:025.0/255.0 blue:147.0/255.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:0.0 green:118.0/255.0 blue:186.0/255.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:153.0/255.0 green:25.0/255.0 blue:94.0/255.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:181.0/255.0 green:23.0/255.0 blue:0.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:255.0/255.0 green:147.0/255.0 blue:0.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:250.0/255.0 green:226.0/255.0 blue:50.0/255.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:255.0/255.0 green:255.0/255.0 blue:255.0/255.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:255.0/255.0 green:255.0/255.0 blue:255.0/255.0 alpha:1.0].CGColor,

                                                 (__bridge id)[UIColor colorWithRed:250.0/255.0 green:226.0/255.0 blue:50.0/255.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:255.0/255.0 green:147.0/255.0 blue:0.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:181.0/255.0 green:23.0/255.0 blue:0.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:153.0/255.0 green:25.0/255.0 blue:94.0/255.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:0.0 green:118.0/255.0 blue:186.0/255.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:1.0/255.0 green:025.0/255.0 blue:147.0/255.0 alpha:1.0].CGColor,
                        (__bridge id)[UIColor colorWithRed:1.0/255.0 green:025.0/255.0 blue:147.0/255.0 alpha:1.0].CGColor,
                                                 (__bridge id)[UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:1.0].CGColor] ;

                        gradientLayer.type = kCAGradientLayerConic;
                        gradientLayer.startPoint = CGPointMake(0.5, 0.5);
                        gradientLayer.endPoint = CGPointMake(1, 1.0);

                        // Circular mask layer
                        CAShapeLayer *maskLayer = [CAShapeLayer layer];
                        maskLayer.frame = gradientLayer.bounds;

                        CGMutablePathRef circlePath = CGPathCreateMutable();
                        CGPathAddEllipseInRect(circlePath, NULL, CGRectInset(self.clockView.layer.bounds, 10.0 , 10.0));

                        maskLayer.path = circlePath;
                        CGPathRelease(circlePath);

                        gradientLayer.mask = maskLayer;

                        // second, smaller circle
                        CALayer *gradientLayer2 = [CALayer layer];
                        gradientLayer2.frame = gradientLayer.bounds;// CGRectMake(0.0, 0.0, self.clockView.bounds.size.width / 2.0, self.clockView.bounds.size.height / 2.0);
                        [gradientLayer2 setBackgroundColor:[UIColor darkGrayColor].CGColor];
                        [self.clockView.layer insertSublayer:gradientLayer2 atIndex:1];

                        // Circular mask layer
                        CAShapeLayer *maskLayer2 = [CAShapeLayer layer];
                        maskLayer2.frame = gradientLayer2.bounds;

                        CGMutablePathRef circlePath2 = CGPathCreateMutable();
                        CGPathAddEllipseInRect(circlePath2, NULL, CGRectInset(self.clockView.layer.bounds, 20.0 , 20.0));

                        maskLayer2.path = circlePath2;
                        CGPathRelease(circlePath2);

                        gradientLayer2.mask = maskLayer2;

[]1