Iphone 围绕多条路径的内边缘绘制辉光
如果我通过将左图所示的两个循环路径相加来创建一个CGMutablePathRef,是否可能获得仅表示右图所示外部边界的最终CGPathRefIphone 围绕多条路径的内边缘绘制辉光,iphone,ios,quartz-2d,cgpath,Iphone,Ios,Quartz 2d,Cgpath,如果我通过将左图所示的两个循环路径相加来创建一个CGMutablePathRef,是否可能获得仅表示右图所示外部边界的最终CGPathRef 谢谢你的帮助 您需要的是贝塞尔路径的并集。苹果没有提供任何用于计算路径并集的API。这实际上是一个相当复杂的算法。以下是几个链接: 如果你解释一下你想用联合路径做什么,我们可能会建议一些不需要实际计算联合的替代方案 您可以绘制一个相当不错的内部辉光,而无需实际计算路径的并集。相反,制作一个位图。填充位图上的每个路径。你可以用这个做面具。接下来,创建
谢谢你的帮助 您需要的是贝塞尔路径的并集。苹果没有提供任何用于计算路径并集的API。这实际上是一个相当复杂的算法。以下是几个链接:
UIGraphicsPushContext
和UIGraphicsPopContext
将UIKit绘制到任意CGContext
首先,我们需要一个遮罩图像。它应该是仅alpha通道的图像,在任何路径内为1,在所有路径外为0。此方法返回这样的图像:
- (UIImage *)maskWithPaths:(NSArray *)paths bounds:(CGRect)bounds
{
// Get the scale for good results on Retina screens.
CGFloat scale = [UIScreen mainScreen].scale;
CGSize scaledSize = CGSizeMake(bounds.size.width * scale, bounds.size.height * scale);
// Create the bitmap with just an alpha channel.
// When created, it has value 0 at every pixel.
CGContextRef gc = CGBitmapContextCreate(NULL, scaledSize.width, scaledSize.height, 8, scaledSize.width, NULL, kCGImageAlphaOnly);
// Adjust the current transform matrix for the screen scale.
CGContextScaleCTM(gc, scale, scale);
// Adjust the CTM in case the bounds origin isn't zero.
CGContextTranslateCTM(gc, -bounds.origin.x, -bounds.origin.y);
// whiteColor has all components 1, including alpha.
CGContextSetFillColorWithColor(gc, [UIColor whiteColor].CGColor);
// Fill each path into the mask.
for (UIBezierPath *path in paths) {
CGContextBeginPath(gc);
CGContextAddPath(gc, path.CGPath);
CGContextFillPath(gc);
}
// Turn the bitmap context into a UIImage.
CGImageRef cgImage = CGBitmapContextCreateImage(gc);
CGContextRelease(gc);
UIImage *image = [UIImage imageWithCGImage:cgImage scale:scale orientation:UIImageOrientationDownMirrored];
CGImageRelease(cgImage);
return image;
}
这其实是最难的部分。现在,我们需要一个图像,它是遮罩(路径联合)区域外的所有发光颜色。我们可以使用UIKit函数使这比纯CoreGraphics方法更容易:
- (UIImage *)invertedImageWithMask:(UIImage *)mask color:(UIColor *)color
{
CGRect rect = { CGPointZero, mask.size };
UIGraphicsBeginImageContextWithOptions(rect.size, NO, mask.scale); {
// Fill the entire image with color.
[color setFill];
UIRectFill(rect);
// Now erase the masked part.
CGContextClipToMask(UIGraphicsGetCurrentContext(), rect, mask.CGImage);
CGContextClearRect(UIGraphicsGetCurrentContext(), rect);
}
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
通过这两幅图像,我们可以在当前UIKit图形上下文中绘制一个内部光晕,以显示一系列路径:
- (void)drawInnerGlowWithPaths:(NSArray *)paths bounds:(CGRect)bounds color:(UIColor *)color offset:(CGSize)offset blur:(CGFloat)blur
{
UIImage *mask = [self maskWithPaths:paths bounds:bounds];
UIImage *invertedImage = [self invertedImageWithMask:mask color:color];
CGContextRef gc = UIGraphicsGetCurrentContext();
// Save the graphics state so I can restore the clip and
// shadow attributes after drawing.
CGContextSaveGState(gc); {
CGContextClipToMask(gc, bounds, mask.CGImage);
CGContextSetShadowWithColor(gc, offset, blur, color.CGColor);
[invertedImage drawInRect:bounds];
} CGContextRestoreGState(gc);
}
为了测试它,我使用几个圆圈创建了一个图像,并将其放在UIImageView中:
- (void)viewDidLoad
{
[super viewDidLoad];
UIBezierPath *path1 = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(20, 20, 60, 60)];
UIBezierPath *path2 = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(50, 50, 60, 60)];
NSArray *paths = [NSArray arrayWithObjects:path1, path2, nil];
UIGraphicsBeginImageContextWithOptions(self.imageView.bounds.size, NO, 0.0); {
[self drawInnerGlowWithPaths:paths bounds:self.imageView.bounds color:[UIColor colorWithHue:0 saturation:1 brightness:.8 alpha:.8] offset:CGSizeZero blur:10.0];
}
imageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
在Swift 3中有两种方式: 路径代码:
let radius = rect.height * 0.25
let centerX = rect.width * 0.5
let centerY = rect.height * 0.5
let arcCenterOffset = radius - radius * 0.5 * sqrt(3)
let degree:(_: CGFloat) -> CGFloat = {
return CGFloat.pi * $0 / 180
}
let gourd = UIBezierPath()
let circle1 = UIBezierPath(arcCenter: CGPoint(x: centerX - radius + arcCenterOffset, y: centerY), radius: radius, startAngle: degree(-30), endAngle: degree(30), clockwise: false)
let circle2 = UIBezierPath(arcCenter: CGPoint(x: centerX + radius - arcCenterOffset, y: centerY ), radius: radius, startAngle: degree(150), endAngle: degree(-150), clockwise: false)
gourd.append(circle1)
gourd.append(circle2)
let gourdInverse = UIBezierPath(cgPath: gourd.cgPath)
let infiniteRect = UIBezierPath(rect: .infinite)
gourdInverse.append(infiniteRect)
guard let c = UIGraphicsGetCurrentContext() else {
fatalError("current context not found.")
}
c.beginPath()
c.addPath(gourdInverse.cgPath)
c.setShadow(offset: CGSize.zero, blur: 10, color: UIColor.red.cgColor)
c.setFillColor(UIColor(white: 1, alpha: 1).cgColor)
c.fillPath(using: .evenOdd)
c.beginPath()
c.addPath(gourd.cgPath)
c.clip()
c.beginPath()
c.addPath(gourdInverse.cgPath)
c.setShadow(offset: CGSize.zero, blur: 10, color: UIColor.red.cgColor)
c.fillPath()
嗨,罗伯。我想在联合体的内侧边缘周围模拟辉光效果。这是通过剪辑和阴影模糊完成的,但是我需要能够首先剪辑联盟的形状。Rob,感谢所有的帮助,以及产生这种效果的代码。这很好用!这很好,我如何用背景色填充这些形状之外的区域?假设我想要一个
[uicolorWithWhite:0.000 alpha:0.750]
作为半透明背景,并将这些圆圈切掉?@jamone你需要将其作为一个新问题发布,而不是作为评论。我很惊讶这个问题被浏览了多少次。我也需要同样的效果!路径本身也带有半透明的“填充”。